This talk is part of the Fountain Fundamentals Conference, July 10-11, 2013, Kansas City, MO.
ENGINEERING 281: Renovation of Fountains – Hydraulic Considerations by David Peterson
David Peterson: Let’s see, can you guys hear me without the microphone? Alright ‘cause I like to stand up here a little closer to you and not hide behind the podium. One thing I want to point out here real quick. You’re probably wondering what the ENGINEERING – 281 is? That’s a number; I actually am also the Chairman of the Education Council for the Genesis 3 Design Group, which is an educational group for the swimming pool industry, pool, spas, and water features. We actually cover all of it and we have all these classes, actually 124 different programs that we do and a catalogue if you’re interested and really want to get into water. We have design courses, architectural type courses, engineering and construction related programs and also some business related programs for the pool and spa industry and water features. So the “281” really just like a university, organizes this particular program into a group with other ones.
This is just a real simple schematic diagram of a really basic water feature and actually this has never been built but I use it for just explaining some really basic concepts. I think a lot of you are dealing with different aspects of preservation and conservation and you’re not really maybe familiar with the terminology that we might use for the actual mechanical systems so I just wanted to point out a few things here. Starting with the lower pond that might be the lower basin of a multi-tiered water feature or something like that. In there we’ve got a pair of suction outlets and I’m going to talk about some safety issues related to that here shortly. We’ve got some pipes that bring the water over to the pump and the pump pushes the water through the filter and recirculates it back up to the upper pond and this just has a really basic spillway. It’s kind of like some of the features that we saw yesterday, maybe that one at the University of Texas where they had the staining on the big wall but it’s just an upper pond and it spills into a lower pond. This schematically could represent lots of different water features. In this particular case there is just one pump and that pump is filtering the water and sending it up to the top so the visual thing that you see, whatever the spillway might be, is also part primary filtration system. That’s not always done that way and we’ll talk about that a little bit but where you have multiple features, you may want to split off your filtration system from your feature pumps and we’ll talk about that a little bit more.
One thing I want to focus on right now is really these two suction outlets right here. There’s a big safety issue with these and that is what we call entrapment. The problem is that those pumps can be very powerful and can actually hold your body down onto the floor of the body of water, it could pull a limb into a pipe and people have drowned or been eviscerated and other problems with these drains. So there’s actually some laws now. We’ve had rules in the industry for a long time and in some states we’re a lot more proactive with it. It got to the point where some states were pretty lax so when the problems continued, the Federal government stepped in.
In Virginia, Graeme Baker, this was passed into law probably about five years ago now. Baker is actually related to the Secretary of State, James Baker, and since his daughter Virginia Graeme Baker, actually this was his granddaughter I think, was the one that actually died. She was held down at the bottom of the pool and despite all the previous deaths that had occurred, this one happened to occur with such a high profile figure in America that we were able to do something about it. So this Virginia Graeme Baker Act passed and really set up a series of rules for people to follow to make things safe. There are some different codes, I’m not going to get into too much detail about them but what’s happened now is that the Virginia Graeme Baker Act has now trickled down into the building codes so that as you’re building anything with water that’s got pumps, you’re now bound to these new rules to make things safe.
A couple of the rules; the most important one is that for all new construction, you need to have two split drains and the reason for that is if you lay your body down on one of them, the other drain can handle 100% of the flow. In other words, you’re not going to be held down and pinned down by the vacuum pressure of that pump. Imagine if you just had a single suction outlet and you’ve got this pump pulling down really hard, if you lay your body down, you probably won’t get up. There are tricks to it, you can get up. Go ahead, you have a question?
David Peterson: Okay. By the way I encourage questions as I’m going and I don’t need to wait until the end so just, if you have something, go ahead and raise your hand at any time. But the idea here is that where you have the T, you maintain your line sizes and there are rules about what the line sizes should be, and you maintain at least a three foot clearance between these strengths, because the human body, at least 99% of the average human adult I guess, would not be able to bridge their body across two drains separated by three feet. So the idea is that if you lay down on one, the other side can handle 100% of the flow without very much restriction at all, so it handles so much flow that you could just roll or push right off. In fact, the force that you’re limited to in terms of pushing off is 15 pounds. A 15 pound force actually came from some studies in Europe regarding the panic hardware on doors and they wanted to make sure that children could get out of a burning building and so 15 pounds, after they did these studies, that was the force determined that you needed to be able to push a door with no more than 15 pounds. So they just took that same rule and applied it here in this standard.
There’s also some other rules about the depth of the pipes and things like that and the reason why I’m bringing this up for this program is that a lot of historic features do not have these split section outlets. They have maybe just a single drain somewhere. So when it comes time to do these renovation projects, it’s important to look at these code issues and make sure that we’re bringing it up to the new standards to prevent any problems. We just had a project, actually we’re still working on it, in L.A. where they had single suction outlets and they were so big, actually they weren’t very big in planning, they were only about 30 inches by 30 inches, but they were about six feet deep and the first time we went out there to look at this project, I thought well what happens if you fall in head first into that thing? There’s not even enough room to turn your body around to get out, so you’re gone, you’re just done. The interesting thing about that project was that they actually had these big stainless steel baskets that were required to be lifted out for maintenance and I thought all someone has to do is lift that out and slip headfirst and they won’t get out. So there’s a lot of little things to think about in terms of safety and this was an old water feature that had been done back in the sixties and they’ve already demo’d out that problem and we’ve got it solved with our new design but these are the kind of things that are really important from the safety standpoint.
Question: Does water depth matter, I mean if you have a shallow pool, are you still required to have the same two drains?
David Peterson: Yes. In fact, this isn’t in the code but it’s in my company’s policy, is that if it’s in a shallow body like shallower than 18 inches, we actually split it twice. In other words, we would have four drains and the reason why I put that rule in place for us is that I’ve seen my own kids at the local club where they’ve got a real shallow pool and the kids, it’s like the use the drains like part of a game or something. It’s like, “Hey Johnny, you go stand on that one, and you stand on that one.” Well you know if two people lay on this, they could get pinned down. The code wasn’t meant to prevent multiple people from lying down, it’s just really for the single person. The chances of two people going and laying down on a drain are pretty remote. Yeah?
Question: What is the distance between the two drains, the minimum distance again?
David Peterson: It’s actually three feet and you’ll see in this drawing it says 36 inches minimum, 72 inches maximum. Actually there’s a couple different codes. Once of them says 36 inch center to center on the pipes. The problem is that the other code doesn’t say center to center so if there was ever a legal problem, the attorneys might bring version out and argue that it was supposed to be 36 inch clear. So I just avoid that whole issue and just say hey, its 36 inches clear. The 72 inch maximum actually this is just in our detail, the reason that I have that in there is that if you put the drains really, really far apart you’ll have more head loss in the lines, more friction, and that will actually create a higher pull down force in the drain that’s blocked, so actually having them too far apart can also be a problem because there’s more head loss and that creates a pressure differential which is your pull down force.
Fran Gale: Some of us are used to working on historic buildings and their issues with code compliancy and there’s a requirement on many projects that when a restoration project takes place, that you’re required to bring the building up to code with regard to fire sprinklers and life safety. Is there a requirement, when you talked about it, it didn’t sound as though…
David Peterson: There is, and actually the requirements came in a couple of different levels. There was one really critical one which is that there was hard date where every commercial project was required to have code compliant drain covers and when they set that deadline it was only about 18 months out from when they passed the law and the problem was that there wasn’t a single drain that had actually been approved to other standard, there’s another, it’s now on the ATC but at the time it was an ESME standard for the actual testing of the drain covers and there were no drains available at the time so it was like the whole industry was scrambling to figure out what to do. That deadline actually slid a little bit and lots of products did get approved and then there was a big push with all the hotels and commercial projects to get drain covers on. But the drain covers only one piece of that puzzle because if the plumbing isn’t done right, the drain cover isn’t going to solve every problem. It might solve certain types of entrapment, there are five different types and it might solve one or two types but not all five. So if there are some work arounds for the single drain problem, if there was no way to get split drains, there are some other solutions. I don’t recommend any of them. Probably the most common one is to put in what’s called an SBRS which is a suction vacuum release system but that’s a mechanical device back at the equipment area that is supposed to sense when there is an entrapment and then it shuts down the pump or it opens up the pipe to break the vacuum. The problem with that is that it’s an electromechanical device and all devices eventually fail so at some point you run the risk of the one safety device actually not working when you need it. So I’m not a big fan of those but we have used them. Sometimes, there is just no other solution to it.
A couple things; these covers and the pipes and the whole configuration is really a design for a specific flow rating and the covers are approved for specific flow ratings. Those ratings are actually printed on the molded covers if you’re doing custom covers then there’s kind of another set of rules that you follow but one of the things when you start dealing with multiple pumps is that if you have multiple pumps pulling from under the same covers, you have to add the total flow rate of all the pumps together and size the systems for that flow rate. You don’t just go by the largest pump or whatever, you have to assume that every pump is running and you have to design for the worst case scenario. Any questions on the suction outlets
Question: What’s this status of trench drains?
David Peterson:Those, we’re using a ton of them. The issue with the trench drains is that they’ve; are you talking about the smaller molded ones or the bigger custom made ones?
David Peterson:The problem with some of the channel drains, the molded ones is that at least one company had some problems with their tests so really the numbers that they were publishing for their flow rates were not accurate and so they had to go back and retest and that actually lowered the ratings. There are other companies that didn’t have that problem and we’ve always specked the other company. I wrote an article probably five years ago about the testing problem and predicted that they were going to have the big recall that they did about two years ago. The problem was is that there is a standard that the companies were testing all these covers to and there were just some loopholes in there, so I did write this article on it that said, “Hey you know, we’re going to have problems because there’s too many ways to work around this,” and one of the companies exploited that actually and made a lot of money doing it. The last I heard they probably made about 100 million because of the issue but I heard that they lost about 15 in the recall. So there were several covers that were actually recalled. So here the industry is trying to run out and replace all the pieces and get everything compliant and it’s like take it all out and start all over. So the industry has had some issues but I think they’ve been solved now and the ratings that are published are good and the testing has been cleaned up. As far as the bigger channels go, like for larger commercial pools, what we’re doing is fiberglass grating as the covers. That process really hasn’t changed. Those covers need to be improved by a licensed engineer and those products haven’t changed and I haven’t had any issues with that.
I want to run through some other devices here and how they might apply to these fountain renovations projects. In that diagram, I didn’t have a skimmer in there but I wanted to show you one. This is a product made by Crystal Fountains. It’s actually a really compact skimmer. It doesn’t handle a whole lot of flow but it’s designed to fit within a thin wall and on some of these features where we have thin walls with small basins raised above grade, you certainly don’t want to have a big bump out for a traditional pool skimmer but pool skimming is actually really good for the water. All your debris basically enters at the surface even if it is a dirty guy taking a bath in the fountain. As he enters, the dirt is hitting at the surface and as leaves are falling they are hitting the surface and if you can get that stuff skimmed off before it gets soggy and sinks to the floor and then just sits there, you can actually keep the systems a lot cleaner. So some of our projects where we’ve renovated old fountains, we’ve actually added skimmers into the walls to try to draw off some of that debris before it gets in there. It’s not going to work for every project. There are jobs where the materials and the configurations just aren’t going to allow for it but there are solutions to make the systems a little bit more maintenance free, like getting the debris off at the surface.
Piping, plumbing materials, on these old systems I see a lot of cast iron, a little bit of steel and a lot of copper. The problem with all three of those is that they tend to foul up a bit more, they rust, cast iron is like arteries or something, they keep closing in until they just don’t flow anymore. Copper also has the problem of having wear on it. Copper pipe is actually pretty soft material and the flow rate that you can push water through copper pipe is actually less than you can do with even PVC because of the erosion of the pipe. In fact with PVC you can move water through it at easily eight feet per second and not have a problem wearing out pipe. But copper, depending on the temperature actually the maximum is five feet per second. That’s what the copper pipe industry says will prevent the wear. At higher temperatures, that rating actually comes down even lower. So sometimes a copper pipe you can’t even run half of the flow rate that you can through an equivalent PVC pipe. PVC and copper, the copper sometimes only handles half of the flow rate of the PVC. What happens with a lot of copper pipes is that the systems are just running too fast, it will wear holes through it, so you have to pressure test the pipe and you find out that you have a lot of leaks which of course, will require replacement. There is really no good fix for that. You can’t just go in and line the pipe because if it’s got holes in it, the lining pipe system is not going to work.
PVC handles chemicals really well, so that’s probably the primary pipe material choice for any new construction. With flanges and things you can certainly swap out existing metal pipe for PVC pipe. It gets a little more challenging if you have exposed plumbing in a basin or something like that. We saw some photos of those details yesterday where we had maybe bronze nozzles coming off of a head or sitting right in the pond. You wouldn’t want to do that in PVC without a lot of other details to hold the pipe in but you know you could put concrete in the basin or something like that to encapsulate it. It doesn’t like sunlight very much so you want to have it UV protected.
Question: Do you regularly spec schedule pressure dependent 40 or 80?
David Peterson: Usually schedule 40, sometimes schedule 80, it just depends on the project, depends on the budget because schedule 80 can be twice as much depending on what you’re doing. And I’ve heard of a few problems with schedule 80 also but really they’re pretty flexible and if you’re designing the systems appropriately, you’re not going to have problems even with a schedule 40. If you have anything that might be exposed to the sun, I say definitely go schedule 80 and then prime it and paint it too. For things underground, I think schedule 40 is fine, even if it’s in a freeze thaw area, as long as you‘ve got your appropriate insulation and your annual maintenance or draining or whatever you have to do.
Question: What about the connections between PVC and Polyethylene? I’ve worked on trying to get small flexible copper up through a frog’s mouth and I would have loved to have gone to plastic.
David Peterson: Right. Yes, you might have a better chance of doing that with the polyethylene because it’s a lot more flexible. One thing I like about polyethylene is that nothing likes to stick to it. It’s almost like Teflon. We’ve had projects where we’ve had like mineral springs water that would just calcify up and block a pipe but with the polyethylene you could just shut off the water for a day and let everything dry out and everything just falls of the pipe and you turn on the water and it flushes it out and everything is clean again. So for those occasional projects where you have really hard water polyethylene is actually better than even PVC. There was a question in back.
Question: What about stainless steel for new piping. I know it’s expensive but it’s a small area.
David Peterson: Yeah and sometimes that’s required for certain details, sure. We try to find ways to avoid getting into exotic stuff unless there’s a budget or an absolute need for it. We can usually find ways to work around that. Some projects do require stainless steel in certain areas of the project but usually not all of it. Maybe the equipment area can be PVC and something that you see out at the feature might be stainless steel.
I think I have a slide on equipotential bonding later which is really an electrical issue but some fountains, the old ones don’t have a dedicated bonding system and for safety purposes the metallic piping might be their only actual bonding method. So if you start taking that out and replacing the PVC you may lose your bonding equipotential bonding grid.
Question: What is that? You need to define that.
David Peterson: Yeah, what it is if you got water in a vessel, whether it’s a water feature or pool or whatever, you have the potential for having voltage differentials between the water and some surrounding metal or the ground and that voltage potential is a shock hazard. So you may touch the water and you become the conduit for discharging that electrical current and it could kill you. So what you do is you have the vessel has steel in it usually, for reinforced concrete stuff, if it doesn’t have steel then you would have a bonding grid. It’s really copper wire like little No. 8 bare copper wire around the feature and you have that linked with the same bare No. 8 copper back to the equipment and all the equipment is all linked up. So what happens is everything in the system mechanically is all tied together with these copper wires and it’s like grounding but it’s not grounding. It’s what we call bonding and the whole idea is that that copper wire will dissipate any voltage potential and eliminate the shock hazard. So if you have stray currents from a motor or something like that, those aren’t going to travel over and build up at the pool until you become the release for that shock. That’s the equipotential bonding and the National Electric Code in Article 680 talks about this. Actually in 2008 it got expanded quite a bit and the rule that’s been in place for a long time now has been that every metal within five feet of the water needs to be bonded. So if you’ve got a water feature and you’ve got a wrought iron fence that’s five feet away, that wrought iron fence needs to be tied electrically back to this bonding grid. If you’ve got a water feature and it’s out on the lawn and there’s no other metals around, you actually have to have a perimeter of this wire running around the feature in the ground to dissipate the energy in addition to having a wire go back to the equipment wherever that is.
Question: So if you have the Calder sitting in the pool, the Calder has to be bonded.
David Peterson: The Calder better be bonded, absolutely. Yes?
Question: What’s the law?
David Peterson:The National Electric Code (NEC) Article 680 and I may have the specific section in Article 680 in a later slide. It’s important for all these metal features too, even if the statuary is a bronze feature it needs to be bonded for safety reasons. I have a slide on that later.
So just keep in mind, if you’re taking out metal pipe that may be the only bond on these older systems so you need to think about how you’re going to re-bond it.
I actually just threw this in this morning. It wasn’t something I thought about before yesterday but the topic of theft prevention came up and I was thinking about some things that we’ve done in consideration of theft. A lot of lights in features they have these lights on bronze stands and there’s just a cord that goes down into a conduit through the floor and usually there’s a coil of this cord around the stand because by code, also Article 680, you need to be able to lift the light out of the water, uncoil the wire, to change the natural light bulb in there and the problem with these stands is that it’s so easy to go grab one and cut the wire and run and you’ve got pounds and pounds of bronze that you can sell. We’ve gotten away from this for a long time, not only because of the theft but because I think they’re unsightly and we have better options and the option that I prefer is that we actually have a niche built into the floor or into the wall and there are light fixtures made by this same company, this is Hydrel, where the light can still tilt, use still have some adjustability, you can rotate it, tilt it up to 30 degrees or something but it’s really locked into the floor and it needs special tools, you don’t see the cords, it makes maintenance of the features a lot easier and no one is going to be able to just go in there and grab it, cut the cord and run. I’ve seen features where you’ve got hundreds of these things out there and in an hour somebody could make tens of thousands of dollars, I’m sure stealing these.
Also a kind of new technology, LED lighting. The colors are getting better; they’ve got warmer colors now. Things are quite so blue and the fixtures are getting really small. They’re so small that you don’t even really need a rock guard on them anymore. The code says that if you’ve got something in the floor, you need a rock guard over it so somebody doesn’t step on it and break the glass and have their foot go through it. These LED lights are getting so small they fit in a two inch conduit or an inch and a half conduit and you just don’t need those big bronze rock guards anymore. They’re easier to install in renovations because you can core through the walls and add these little lights as opposed to getting a jack hammer out and breaking large holes and dealing with all the reinforcements, so that’s another option that you may want to consider.
Bronze nozzles, we actually did have a water feature up in the Bay area that we did a few years back where it required some renovation and we ended up putting the nozzles actually in concrete. It’s sort of like the Calder project where you raise the floor. We had the same thing. We didn’t want to take the floor out so we needed to re-plumb it and we came up with a detail and we used a certain nozzle from Crystal Fountains that can actually be in the concrete itself. So there was no chance of anybody stealing it, so I threw that in.
Unknown: By the way, as you were talking about the bonding, I remember that because the last time before the renovation, all the washers and bolts that were holding the pylons in place were all corroded. We actually put in a nautic system underneath it as well, so that should take care of any open potentials as well, I would think.
David Peterson:Yeah and things that are not bonded actually will rust a lot easier. We do a lot of custom stainless steel covers and things and there was a project in L.A. where the builder put in probably a dozen of these stainless steel covers, and one of them for whatever reason was just rusting up far more and the other ones weren’t even rusting. One of them was really rusting up so they drained the pool and researched it and realized a bonding wire had actually broken for that particular unit. It snapped off and so they cleaned it up and re-bonded it and I think it will be fine.
Moving down our schematic diagram is pump technology. Variable frequency drives have been around for decades but probably very few of them have really been used in historic water features. The technology just wasn’t available back when they were done. What a variable frequency drive does is it takes the power or the frequency of the power going to the motor and it adjusts it so that the speed of the motor can vary. When you plug in a pump into the wall, the standard frequency is 60 hertz in the U.S. but the standard speed that that rotates at is about 3450 RPM. There are slower speeds like half of that but for the most part, it’s a fixed speed and your pump performance is based on that speed. With this technology, by varying the frequency going to the motor itself, you can speed the pump up, you can slow it down, and you can dial in the performance of that pump to match the hydraulic performance required to the project.
The first thing that that has a potential of is a lot of energy savings. You can actually save a lot of energy by slowing down the water to just what you need. You can maintain specific flow rates, we’re talking Ricardo’s project where the clean filters everything ran fine and as the filter dirtied up everything died down. This pump down here would actually sense that and speed up. So you might start at half speed and as the filter got dirtier the pump would just keep ramping up and ramping up. At some point it’s going to get it to blow up. At some point it gets up to 3450 and it just can’t go any faster and then you’ll start to see things slow down but that, maybe that spans a couple of weeks before you have to change the filters. We’re going to talk about the filters in just a little bit.
When you slow things down they get quieter, everything lasts longer and the motors that are used are three phase motors which are more efficient than the
other motors. We’ve used these on all motor sizes up to 50 horsepower and you can get variable frequency drives for any size motor. This unit down here is actually a common pump in the pool industry and what’s happened is that the expense of variable frequency drives has come way down and now the sales are coming up so the price point is really tolerable for these smaller sized units. You can actually buy this pump for like $1100 dollars. It’s got the variable frequency drive built right onto the pump, which is really impressive. Just the little boxes used to cost more than that but you can get those things now for a couple hundred bucks and you can add that to existing three phase motors that are out there so as you’re redeveloping things, that’s a great tool for providing more control over the system.
There was another project yesterday where somebody talked about when the toilet flushed the water would squirt out further, well if that water was controlled by a pump like this or a variable frequency drive, you could actually have a sensor that just monitors the pressure and just kept it at whatever you needed, whether somebody was flushing the toilet or not the pressure would be constant. Those are the kinds of things that you can do with variable frequency technology.
Filtration; there’s different products out there or different methods or media for filtration. We use a lot of sand for commercial projects. I like it because I can automate the backwash. You can clean the filter without having to take anything apart, in fact I can do it electronically from an iPad if I wanted to by just putting a motor activator on the backwash valve. Especially for water features, the clarity of the water is great in fact; some of the best water clarity I’ve ever seen is from a sand filter despite the stuff on the internet saying that it doesn’t filter down as fine as DE or cartridge. I can make it work as good as DE or cartridge.
Cartridge filtration; Ricardo showed a photo of what that looked like. You’ve got a housing and there are one or more cartridges in there and you take the cartridge out and clean it and put it back in or you replace the cartridge and the problem with those is that it’s very labor intensive. I would say for your project what I would do is look at doing sand filtration and automating the backwash and there’s some rules about how fast that water should go through there but I know you can handle the goose feces with that system, in fact the sand filters, that we still do zoological projects, we’ve done projects for Sea World and Shamu poops too and this is how we filter it, right? So it’s the only way to do it. You’d never want to do that with a cartridge filter so it’s just a wrong technology for that particular type of …
Question: Would you need a bigger vessel for the sand?
David Peterson: Yeah, yeah you would need a bigger vessel but it’s still, the bigger vessel is what solves all the problems because I can keep all the debris right on top of the filter and then just have it backwash out and I don’t have to get in there and do anything with it.
Question: So for a fountain the size of the one that we saw that you had trouble with or the other metallic fountain, how big would this be and do they have to maintain it? I mean obviously do they have to clean out the sand? Where does this all go?
David Peterson: Well what happens is the water; the debris actually comes in the top of the filter and spills out. So imagine here you are coming down and the debris starts collecting at the top of the sand and your clean water comes out the bottom side. To backwash it you’re actually pushing water up through this way and it takes all the debris and sends it out at the top and throws it away. So when you do that you’re throwing away some of the water out of the pond or you can set it up to backwash with fresh water if you wanted to so your wouldn’t throw away any water.
Fran Gale: Where is it throwing?
David Peterson: Into the sewage.
Mary Striegel: So you’d have a waste line that you’re backwashing into a waste line?
Fran Gale: Like a sanitary solution.
David Peterson: Yeah a sanitary solution, right. Especially if there’s goose poop in it.
Question: You were talking about skimmers and being able to skim off leaves, is that system going to be able to deal with that large floating or is it going to get masqueraded in that process?
David Peterson: It will. If you have leaves though, I would say that you want a pump that’s got a strainer in front of it either an integral strainer or you put a separate strainer in front of the pump and try to catch some of the bigger debris because you don’t really want that going through the impeller of the pump anyway. You could do an open impeller pump and there are certainly pumps that handle debris that can handle up to two inch diameter solids fairly easily. I would rather not send that stuff into the filter if I could catch it ahead of time with a strainer I would do that. I believe the story was that the goose stuff was just too slimy, it’ll go through a strainer and I understand that. The worst thing I ever dealt with was hippos actually because they’re waste is like, they always do it in the water, and it explodes and it’s like made out of grass and everything just floats and you just want to junk the whole thing and start all over again. I’ve never seen anything worse than hippo poo.
Biological filtration is using bead filters. This is what we use on a koi pond or some kind of fish system. Strainers, we just talked about that. Centrifugal filters are, with that is imagine if you have a cone and you take water in tangentially into the cone and its spun around, the heavier debris is going to fly out to the outside where you can actually take it out of the system and get rid of it and the lighter stuff which is hopefully just the water comes out the bottom and moves through the system. We’ve used that to separate sand from water, even before it even gets into the pump, just automatically throw away the heavier debris. Depending on what the application is, you have to select the right technology for treating that water.
Chemical monitoring; this is an example of a chemical automation system, everything, every project we do gets some kind of chemical automation on it. Most of our projects, if it’s a fish system or something like that where you’re not putting any chemicals in it. The way to think about this is it’s like a thermostat for your heater. You have, in this case, we’re monitoring two different things, so there are two different probes but one of them is monitoring the ORP, the oxidation reduction potential of the water. That’s really an indirect measurement of any oxidants in the water, like chlorine or ozone, bromine, and you have a set point and that’s measured in millivolts, so you might set this at let’s say 700 millivolts and if the pool or whatever the body of water is, when it drops below that set point, this system powers up a pump. So one of these lines is power in and one of them goes to like a medical pump or something or a peristaltic pump and it just injects chlorine until the set point is achieved until you get back to 700 so it’s just like a thermostat setting the temperature in a room.
The other probe would measure the pH of the water, so you don’t want the pH to get too far away from the ideal set point or it’ll damage the materials, so you set it, usually if you’re adding chlorine what tends to happen is that your pH climbs and the fix for that is too add acid so you would have an acid feeder on here and you would set your pH at say 7.2 to 7.4, which is the pH of your eyes and if the water pH matches the pH of your eyes, your eyes won’t burn when you get in the water and then it just automatically feeds in a little liquid acid or something. There are different things you can put here; I mean you could have a generator that kicks on or some other granular feeder for granular chlorine.
Question: Those probes, how much maintenance and calibration do they require?
David Peterson: Well about every two months, you want to clean them, take them out and do a cleaning on them. They only last about two years and that kind of depends on some environmental things you know, how bad is the water chemistry going through it all the time, is it going through too fast and just wearing out the KCL neck. There’s actually a little porous, there’s a chemical in there, think of it like a battery. I mean that’s really the best way to describe that. There’s actually a chemical in there that actually has to leak out and it’s a reference chemical and the probe is comparing that reference to the actual water chemistry to determine what the chemical range is. So eventually the probe runs out of the KCL. Yeah?
Question: Is that two years with daily operation or is that a twenty-four month period where as you run it four months, four months, four months over probably three or four years but taking care of it in the off season?
David Peterson: Yeah, you could make it last longer if you are only running it for four months a year. You would want to take it out and then store it, submerged in the KCL which is really what’s inside of it and they’re not terribly expensive, they’re $100 bucks or something.
Question: How much for the system, in general?
David Peterson: There’s a range. I’d say they probably start at $600 and go up to a couple thousand bucks for one that talks to the internet and records the data. A lot of hotels will use one that actually records the data internally because they’ve had that experience where some guest calls them up on Monday and says, “ I want my bill wiped out because I got sick in your spa,” and then they go print out the report and go, “No, the water was good, I’m keeping your money.” So they spend a little more.
Question: So the internet ones are the ones that can actually be controlled remotely?
David Peterson: Yeah, right. Yeah you can monitor them remotely and even feed chemicals remotely. Is there another question back there?
We talked a little bit about UV yesterday and I won’t go into too much detail but this is just an example of a system where you’ve got water flowing in one side and flowing out the other side and it goes past a UV lamp that inactivates any bacteria in there.
Question: Question. Do you inject your chemicals after your UV?
David Peterson: Yes.
Question: If you have to put acid, would I have….
David Peterson: Yeah, usually I do because UV destroys chlorine. Now they say that in the short time that the water is flowing through there it’s not supposed to be a problem, but still I like to have it after that, have the chemicals injected after that.
Ozone; I’m a big fan of ozone. This really came from my experience with the water park and the zoos, the Sea World type clients out there because they can’t use chlorine. You can’t put chlorine in Shamus’s tank. It’s a priceless animal so what we do instead is we inject ozone into the water in high concentrations. That ozone just nukes the water; I mean every pathogen is killed. As it reacts the ozone reverts very quickly back to oxygen and you can strip off that off oxygen and strip off any excess ozone and run it through a destruct unit, I think I have a schematic diagram of it. In this case we’re showing that we’re using a pump and then we’re injecting the ozone in. We’re actually running it through this contact tank and the goal of the tank is to achieve a certain CT value, it’s a concentration multiplied by the time that it’s in there, so the concentration comes from how much ozone you’re injecting relative to the flow rate and then the time of course is related to how big that vessel is and certain CT values are known to kill off certain pathogens like giardia and other recreational water illnesses that there’s certain CT values that the EPA has said , “Hey, this CT value will kill that, “ and then by doing this what ends up happening is you get this water that’s been nuked if you will, and any excess ozone comes off of there, so hopefully what’s going up into the vessel does not have any free ozone that you’re going to smell, nothing out in the vessel.
I think for you guys this contact tank is really important because I actually would not want the ozone, the ozones are a very strong oxidant. I wouldn’t want near any statues or plants or anything like that because it can damage things. Yeah?
Question: So this works similarly to the UVC where it’s only effective if whatever you’re trying to kill is actually flowing through the water, if it’s attached to the wall of the fountain or whatever, it’s not going to do anything because we can’t reach it?
David Peterson: Right, right. Now that being said, we’ve actually done systems that are chlorine free and they just run on ozone and you can’t smell the ozone but you can detect it in the water. Normally with ozone you would want to maintain a residual of chlorine in the water. You could reduce that instead of having two parts per million chlorine, you could be down in a half a part which would be much better for you because you’re going to let the ozone do all the work back in the filtration system and assuming that you’ve designed it correctly and your system’s efficient, this will handle it.
Question: What’s the frequency of the injection?
David Peterson: It’s continuous yeah, it goes on generator. Because the half-life is measured in seconds you have to generate [ ? ], you can’t produce those on an [ ? ] somewhere like in a bottle. You generate it right on site. One way is with the UV systems. I prefer the Corona Discharge because the concentration is a little higher and I think the systems last a lot longer with proper maintenance. Yeah?
Question: Can you describe a little bit how the trap works, the ozone trap.
David Peterson: Ozone trap, hum…
Question: You have it in your drawings for construction.
David Peterson: Yeah on this side here? Okay. The ozone destruct unit is really just like a bed of granular activated carbon. As soon as the ozone hits it, it just turns right back to oxygen. Inside there, now there may be moisture coming up through there because the ozone just left the water, and there may be water that gets up into the system, so there’s usually a little heater in there to keep the carbon dry and to make sure that we don’t get any water up there, we have this water trap detail and actually the manufacturers basically have it down to a little part that you buy now and you just plumb it in and what it does is it ensures that if any water got up into the system it would actually fall out and go through a drain as opposed to going up into the unit where you’ve got the carbon so that guarantees that you’re not going to have an issue with the off gas.
Question: What maintenance is required then?
David Peterson: Nothing. There’s no maintenance on these systems. Every few years you may have to change the carbon in that system but there’s no regular maintenance for that. The maintenance for the ozone generator is every few months you want to clean things up. Some companies say once a year you actually want to dismantle the corona discharge cells and clean them out and reassemble them. It’s basically a chamber of lightening if you will. That’s how creative it is with the dielectric and it just creates lightening in a tube.
Question: And if there is a mechanical failure, how do you know that that is happening?
David Peterson: On the other generator, there is, you know depending on the model of course, but there are indicator lights that tell you if this has got power and you can use those on monitoring devices, you could use the ORP sensors that we were talking about to tell you if it’s actually working. When we put these in a closed room, if we have a lot of ozone, we’ll actually put in a little wall mounted air quality monitoring thing that just sniffs for ozone like a smoke detector would and it alarms if it detects ozone in there just in case you have a leaking tube or something because you wouldn’t want to breathe it. You’ve all smelled ozone before if you’ve ever been in like a FedEx, Kinkos and they’ve got all the copiers going, every time those copiers flash, they’re creating ozone, so if you ever walk in and kind of get that sweet pungent smell of the copiers running, that’s ozone. But in those concentrations, you know you’ll see actually on some of the bigger copiers like a tube going up to the ceiling because they’re trying to vent it off to not breathe it all day.
Question: On the ozone, the destruct unit, now does that have to be vented off or can that be just vented into a room?
David Peterson: Yeah, that can be vented off. We usually vent it outside the room but the only thing coming out of there is just air. Yeah, there’s no more ozone at that point.
Question: One thing I’ve seen particularly on indoor fountains and often the plumbing is done in such a way is that you actually get terrible water circulation. You’ll get a single stand pipe which is the return line and you get very little mixing the water within the basin and you get dead zones where, you know the question I’m having, to get the return water or the water in the basin well mixed, to be able to return things, the bacteria, the sludge it often that the plumbing design on the return line doesn’t accommodate a good circulation within the bowl and so you I always get the sense that you’re cleaning the same water again and again. It’s just right at the surface.
David Peterson: Yeah, the system is short circuiting. Yeah that is a problem and it’s important to try to design those issues out. Actually I just ran out of time so I’m going to run through the rest of these pretty quick.
Salt systems; you’ve heard of salt. It’s really a way to make chlorine in a pool. I do not recommend doing this anywhere. The salt will destroy everything eventually.
Descalers; we talked a little bit about this yesterday. On the magnets, the reason I was asking about it is I had a client that had a little scum line on his pool and he bought some of those magnets, the scum line was there for years it was like calcium. He bought some of those magnets, clamped it around the pipes in the equipment area and in less than four weeks the scum line disappeared. It was like, that really worked and it was just magnets. Then there’s electronic versions of that but that’s the only experience I know and I was just wondering if anyone here knew anything about it.
Ionizers, copper and silver; the problem with those I think is staining. I don’t recommend those. There’s also a lot of products in the industry. I generally call it magic pixie dust, everyone has their secret formula and they say, “Aw, you put this in and it will solve all your problems and it won’t eat chlorine anymore.” The problem is that it doesn’t work. None of it works nearly as good as chlorine. They all raise the total dissolve solids, which I think is bad. It’s one thing that’s so great about the ozone is that the by product is oxygen right, so it keeps the TVS low. Ozone is pH neutral so you’re not having to add a bunch of acids with it.
Automatic field devices; with hard water what we’ve been doing is putting in RO systems and we never fill the pool with that because it will just etch the materials but fill the system with good water and we have the option to basically bypass the regular fill and run water through the RO. You might do that for a month and then run you’re testing to see where you’re at with your hardness and TVS and then you can switch the valves back and shut off the RO and by just checking it on a monthly basis for the amount of water that’s used for a lot of vessels, it actually works out pretty good and it keeps things in check. You don’t want to have to throw away a bunch of water.
General control systems; this is just controllers that schedule lighting and the pumps and all that stuff. These have gotten a lot more advanced. The communication technology has gotten a lot better over the last five years or so, so that you can monitor these things remotely from your iPad or whatever, you can have multiple bodies of water monitor all your desktops so you can see what’s going on out there. We’ve got a project in the Bahama’s where we actually have cameras and sometimes we actually have to look at the cameras to figure out what’s going on.
A quick project, I will run through a few photos. This was a water feature in Montecito in Santa Barbara. It was built about 1915 or so and originally the water flowed through this, it was fed from a natural water fall and there was no recirculation system. The water started at the far end, there’s spillways on either side and actually three on those walls on the far back. The water came out of the spillways and then it flowed through each of these little runnels and spilled out of the mouths of each of the different characters. The system actually did not run since the seventies because the maintenance was a disaster. Every little spillway would just clog up with debris. There’s a lot of oak tress here in and so within an hour of operation, leaves would fall in and just jam up the small hole on the backside of the wall just behind the lion’s head there and once it plugged up then the basin would just overflow and then that would cause damage to the landscape and so they just hadn’t been using it.
So our challenge here was to find a way to get this to work with a recirculating system and the waterfall had dried up years ago so, and this property is owned by an elderly couple that didn’t want the maintenance nightmare. I think when this was originally built this estate probably had full-time staff so they could afford to have somebody out there cleaning it up all the time.
What we did is we actually found a way to, we put in a tank underground and multiple pumps and we pulled out the tank and we fed each of those mouths independently with clean filtered water. Then we had a skimmer, basically a custom bronze piece that I designed, which really just had a little slot so as his water would fall over it would just overflow here and all that water would flow by gravity back to the tank. So each system was sort of its own independent little vessel but all shared a common tank, a single set of filtration and chemical treatment systems and we were able to adjust the flows going to each different vessel. So one of the problems here is you can see the staining on that back wall. They had such a little tickle back there that the water was just sucked back to the wall and just dribbled down the wall. Now we were able to actually give it to sheet off and they did some clean up on that wall and a little bit of restoration. Hopefully this will last a lot longer before it destroys that wall.
Question: Where is that wall?
David Peterson: That wall was back up here. That’s really the start of it and this is really the termination here. Now when this was originally done, once the water hit this point, it actually went underground under the house and there’s another series of features on the downhill side of the estate and it all terminates into an underground grotto that you can go and sit in and it’s got like this cooling effect , it’s really kind of neat. But the water just flowed through and once it went into the grotto it went out basically to a storm drain and then flowed out to the ocean.
Question: So on your new design when it shuts off, it doesn’t overflow your bottom pool there or just…
David Peterson: Right and any debris that gets in there actually flows through these little bronze skimmers that we designed and here’s one, I never wanted to do the piles but there were other issues with the vessel, there was a lot of structural issues and cracking and so we had a lot of water creeping details to work out and we couldn’t touch the outsides because that involved the original finish material so the only solution was to put a system on the inside and to hide that we ended up with this. But here’s clean filtered water coming in and everything including the leaves just falls into there and we catch the leaves in that tank. So it really makes all of this maintenance free. All the maintenance is just done where the tank is and you can open the lid, pull out a basket and dump out all the leaves and the weekly pool and water feature maintenance guy can handle all that.
Question: How long has this been in operation since you did the project?
David Peterson: This is now been running for four years.
Question: How is it now? Have you seen it recently?
David Peterson: Yeah, it’s running fine.
Question: It’s good?
David Peterson: Yeah.
Question: Very nice.
David Peterson: Yeah, because we’re only putting clean water up there it’s a…
Question: Where do you clean it out?
David Peterson: I did show a picture of it but there’s an area down the hill a little bit where there’s a tank buried underground where all the water flows to and all the equipment sits on top of the tank.
This might have that code section on, yeah here it is. Article 680.26B1B and that was that equipotential bonding code requirement. And I think that’s it.
Mary Striegel: Thank you. We have time for more questions for David.
Question: What estate was that was in Montecito?
David Peterson: It’s called Kingston Oaks.
Question: I used to live there.
David Peterson: Yeah.
Mary Striegel: Were there questions over here, I thought…Tom?
Tom Podnar: You know on the variable drive pumps you can adjust the speed of the motor and put out certain amount water. The pumps have to run in what they call the sweet spot so that there’s some back pressure against the impeller to make everything run right, so do you still have a valve on the outflow that you can adjust to put out back pressure against the pumps. So I’m just curious how…
David Peterson: Yeah, we’ll usually have a valve there because you may need to isolate the pump anyway. Your pump is probably in a vault of some sort I want to flood its suction for it we probably would have a valve there. But our goal is to not throttle the valves because when you throttle a valve, you’re just wasting energy. You’re creating head and restricting the flow in the pumps trying to overcome that but with the variable speed drives, the way that the variable frequency drives controls the power, you don’t have that problem where you need to throttle the valves. It actually accounts for that when it, it’s not just changing the frequency, it’s changing the power driven to that motor so it’ll actually handle it when you slow it down. You have a new sweet spot for the pump is what happens. Your pump curves actually have one.
I never intended to talk about it but I thought somebody might bring this up. This is actually a series of different horsepower pumps but you could take this pump right here and slow it down and essentially replicate all these versions here. You could take the three horse and slow it down and get the performance of the half horse, so if the sweet spot is here at full speed, you know, you’ve got a different sweet spot if you slow it down.
Tom Podnar: Rather than using a valve to throttle against it…
David Peterson: Right…
Tom Podnar: I see. That makes a lot of sense.
David Peterson: Yeah. And that’s why, you know what happens with the valve is that you’re operating at the wrong spot and you may be operating off the end of the curve and you’re throttling the valve to bring your system curve in line with the sweet spot of the pump and what I would rather do is just slow the pump down until you have that spot, that it’s fine. It’s tricky to try to explain this in such a short time, I need a two day class where we can really get it but…
Tom Podnar: I think you explained it just right.
Mary Striegel: For those of my colleagues here that have ever seen our recirculating wind tunnel, our variable speed bands are identical to this. I mean what we do to control the wind speed in that environmental exposure chamber is exactly the same.
ENGINEERING 281: Renovation of Fountains – Hydraulic Considerations by David Peterson
This presentation focuses on the hydraulic aspects of fountain renovation. We will start with what to look for during the initial site visit and project assessment, and then move to a list of considerations to review during the design. Technology for water treatment and equipment has changed and we will discuss how to implement these improvements and where they should be avoided. Most importantly, safety and code compliance is key and the changes could have a detrimental effect on the project or, with some creative ingenuity, they may enhance the project.
Discuss project assessment, hydraulic tests, and documentation of existing conditions.
Identify hydraulic performance and issues, equipment replacement, and material compatibility with potential water chemistry changes.
Explain important safety considerations, the ANSI/APSP-7 Standard for Suction Entrapment Avoidance, and unique solutions to renovation projects.
Examine code requirements and ways to make old non-compliant projects safe.
Peterson is President/CEO of Watershape Consulting, Inc., an international planning, design, and engineering firm providing owners, architects, contractors, and the legal profession with services relating to residential, commercial, and institutional pools, spas, and water features. He obtained his B.S. Civil Engineering at Cal Poly, San Luis Obispo and is a licensed engineer in several states. Peterson has been in the watershaping industry since 1994 when he began his career designing life support systems for large aquariums and marine mammal exhibits. He was Vice President Engineering at Polaris Pool Systems where he developed and patented several products. He is a prolific writer and is actively involved with trade organizations and code development.