In-Floor Cleaning

In-floor cleaning system on pools are common in Arizona. Not too common elsewhere. A distributor head that looks like an octopus distributes flow from one set of nozzles on the pool floor to another moving dirt along and toward the drain where it is sucked up by the pool pump into the filter for removal later. The dirt gets kicked up of course and technology has changed so sometimes the idea is the nozzles just kick the dirt up everywhere and skimmers and bottom drains take the dirty water to the filter. Its a wonderful concept but it requires a lot more pump power than otherwise. Normally we'll see 2HP pumps on these pools. A pool without in-floor cleaning would only need 1/2 or 3/4HP. The power requirement is threefold higher before we even consider the load. The infloor cleaning system requires more pressure. That means the pump works harder. That means it uses more energy so a pool with a 2HP pump and infloor cleaning running the same 8 hours a day might consume 5-10 times the energy as a pool without the feature. That means 5-10 times the electricity bill.

We are working with a dealer in Tucson at this moment, Kevin, we'll call him. Kevin's PV (photovoltaic solar electric systems for electricity) company just installed a $90,000 solar electric system for a customer and the new pool is getting solar heated as well. The customer is more comfortable with Kevin than the pool company's recommended solar company who wants to put large coils of polyethylene pipe on the roof. Kevin has demonstrated our flat roof no roof penetration ballasted Powerstrip system (not published on www.h2otsun.com yet) to the customer and he's impressed. The problem is the pool company wants to install a 2HP pool pump with infloor cleaning. We've recommended a variable speed pump to minimize operating cost and to allow fine tune adjustment of the pump after the fact so minimal energy is wasted with the infloor cleaning feature. They finally gave in and agreed to this but not without a lot of resistance based on the premise that in-floor cleaning systems need to operate all the time the pump is on. If that is true then there is little electricity savings to be had. What we believe to be the case is that infloor cleaning does not have to be on all the time. Customers we have talked to have reported that 2 hours a day is plenty. With a variable speed pump we can program infloor cleaning to come on for 2 hours near the end or start of the filtration cycle. During these times the load is high but we can minimize it by setting the pump speed just right. With a Pentair VS 3050 (our preferred vfd pump) for example, we have the choice of 3050 different operating speeds. Not only do we get to set the speed just right but at any one operating point the motor on this variable speed pump will be 92% efficient whereas a regular motor on a regular pump is more like 55%. That's the motor. The pump that is attached to the motor also has an efficiency that must be multiplied by the pump efficiency to get the overall efficiency (we call the whole thing the pump normally). The pump part of the pump will be more efficient on a single speed pump because the impeller and housing are designed for that one speed instead of 3050 speeds but the difference isn't as much as the motor. Overall we typically see efficiency 30% better with a VS3050 pump (pump/motor combo) than we do a single speed pump doing exactly the same thing. I have this data straight from the horse's mouth. My friends at Pentair gave me access to actual test data that was done leading to the Title 20 law in CA (Jan 2008) that stated that anything over 3/4HP was illegal on a residential pool (retrofits and new construction). There's talk that variable speed pumps may become mandatory next round. Its socialism I tell you and its the best kind. The pool industry proved that it is incapable of taking efficiency into consideration in their pool designs so Arnold had to step in and terminate their oversizing habits. Now its not just me and a few top pool design teachers spouting off about 1/2HP vs 2HP. Now the pool builders themselves are all about energy efficiency in CA. Not so much in AZ.

Ironically its easier to tie solar into a pool with an oversized pump than it is after we've successfully solved the pressure problem by changing out the customer's pool pump for something sized more reasonably (or gone variable speed). If the pool is simply a pool with infloor cleaning its definitely a pressure situation so we employ a pressure design. Something like case 7 at http://www.h2otsun.com/pk is appropriate. Note that with a high pressure design what we are doing is regulating the pressure. Its easy. We just limit the flow we allow to go to solar. We don't divert flow to solar. The pressure wants to send the water up to solar. The pressure is higher than the roof height. What we are doing is limiting the amount of flow we allow to go to solar and dropping the pressure to the solar collectors. It sounds so easy but its just the beginning because we need to get this low pressure water from the solar panels back to the pool still. We need another pipe that isn't under pressure. Water won't flow from the low pressure solar panels to the high pressure pool plumbing unless we pump it and that would be crazy. We're not adding another pump to force the water from solar back into the pressured plumbing. The best analogy I have ever come up with for this is the kitchen sink. If you open the tap on the kitchen sink you are just opening a valve teed off the pressure line. You aren't diverting anything. The pressure drives the flow from high pressure to low pressure. Once the water leaves the tap its at zero pressure (zero gage pressure equals atmospheric pressure which is 14 psi- zero is atmospheric on any gage). Water flows because it has a place to flow to that is not under pressure. The drain pipe from the sink to the sewer is open so its under no pressure so water flows there. If we tried to force the water back into the pressured pipe it came from it wouldn't flow and the whole kitchen tap line would go under that full system pressure. Note that with no flow the whole thing is under full pressure. You can't regulate pressure without having a low pressure place to return the low pressure water to the pool through. Its a great analogy and occasionally a pool builder stops arguing all-knowingly when this analogy is made and many times we've opened the door of doubt just enough that we start to see an opportunity to win another one over to our side. Our side, by the way, is the side that says we all have a lot to learn from each other and if we are protective and defensive we aren't open to learning anything from anyone. That's old school. New school is the public is smart and has access to this kind of information so you better get with the program if you don't want to get embarrassed by someone like Kevin who admits right up front he has no pool mechanical experience yet there he is making a pool builder with 30 years experience look foolish and costing the pool builder and his gravy train of kickbacks for recommending a truly bad solar company and product, one customer at least. Its unfortunate that the solar guys have to argue with the pool guys in the first place. We are the mechanical design experts and we are the ones who have to take responsibility for a very long time for this large array of thin black plastic expanding and contracting on the roof top freezing in winter to boiling in summer not to mention the rest of the pool mechanical system. Pool builders don't take responsibility if the filter explodes. The solar guys gets blamed and so he should if he is guilty of ignorance. Pool builders need to learn to respect the territory of the solar installer. These days a solar installer has to be responsible for what he installs so he has to follow manufacturer's recommendations. Solar pool heaters need to be designed. In this industry the big players have no standards. They have specs and those specs are surely called on in the event of a major warranty hassle but those specs are not understood by their people in the field. We're writing the book on this. If the pool has infloor cleaning we need somewhere else to deliver the solar heated water. We need a separate pipe to the pool or if its a pool/ spa combo a separate pipe to the spa. Usually there are other inlets to the pool that we can utilize but sometimes not. Think about what makes sense here.



My own personal pool mechanical design premise is that all pool design should start from the idea that the pump needs to be sized right. What has happened historically is that pumps have always been oversized just to be sure. Filtering, solar, salt water, ozone, and vacuuming all require minimal power. 3/4HP is plenty on any residential pool. In floor cleaning, spa jets, waterfalls all require much higher power and should all be on a separate higher power pump that only runs when one of these features is activated. Infloor cleaning would need to have its own filter to accomodate my pool mechanical design philosophy. That adds cost and takes up space so that is no good but I truly believe that if a pool builder simply took 5 minutes to sit down with the customer and give him some choices he'd not only upsell to the better arrangement he'd also eliminate the chance that any of his competitors would win the customer's confidence. In the two pump scenario the job of the solar designer is easy. We just tie in after the filter and divert the flow to solar and return the water before the gas heater. Its Figure 1a in the installation manual you can download at www.h2otsun.com off the navigation bar at the left. The two pump idea never flew well so most pool spa combo pools we run into are single pump systems and that pump is oversized and now that electricity cost (and global warming) is an issue people aren't happy about what the pool company did to them. The retrofit solution is the variable speed pump. In solar /filtering mode the speed is low and electricity cost is low and the pump runs all day quietly. When a higher speed function is called for solar is off and isolated from the pressure by the seals in the 3 way valve as well as the return line check valve and the higher speed kicks in along with higher pressure and everyone is happy..... until the check valve or the 3 way valve leak...We need a failsafe so what we use is a spring loaded check valve. If pressure ever goes too high it'll exhaust water and let you know there is a problem. This is a perfect lead in to my next article which I promise will be a lot more interesting and contemporary. Understanding pressure and flow as it relates to solar design in these first two blogs is absolutely critical. Once you understand what causes pressure and how to solve pressure issues you can tackle any pool mechanical design issue you come across and its really smart to do that before you start adding solar heaters with hundreds of extra feet of plumbing and thin black tubing all over the customers roof. Somebody has to look at the big picture and the pool builders haven't done it in the past so we have to. The situation is entirely different when dealing with commercial pools. There we have design employed. Not so in residential.