Super Pump VS 20x40 Filtration
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This page looks at a large swimming pool in the range of 20'x40' that has 1.5" plumbing lines which is not an ideal setup for a pool. Large pools in the 20x40' range can be 30,000 to 40,000 gallons and that much water volume should have larger plumbing lines than 1.5" PVC as this will be pretty limiting for a pool this large. The problem is that fast moving water moves very inefficiently due to friction and turbulence. The smaller the plumbing lines, the faster the water velocity needs to be for a given volume of water pumped. In short, modern large swimming pools will almost all use larger than 1.5" pipes however there are many older 20x40' pools still in use which do have the limitation of 1.5" plumbing lines. This article will look at how to program a 24 hour variable speed filtration schedule for a pool like this where we need to balance both performance as well as cost.
Ideally, if you were to build a pool specifically for efficient water flow, you might expect to see 3" or 4" pipes sizes (on the suction lines especially) in a residential pool, and commercial pools with greater flow and filtration demands would likely have pipes even larger than this. This really goes to show how far from ideal it is to have 1.5" plumbing lines on such a large pool. I promote that three turnovers of the pool volume every day is ideal in order to achieve 95% of all the water in the pool being filtered at least one time. With a large pool like this unfortunately that means we are looking at upwards of 100,000 gallons per day of filtered water through the system. That is a lot. Fortunately we can still design a 24 hour filtration schedule that will meet and exceed these values while also minimizing on the costs of electricity to run the pump. In short, we will pump as much water as we can through the filtration system while still trying to save some money in the process.
Filtration goals - Three turnovers of the pool volume daily will result in approximately 95% of the water in the pool being filtered at least one time. The first turnover nets 63% and the second nets 86%. The third 95% and a fourth turnover will result in approximately 98% of the water being filtered at least one time. This is due to how the clean, filtered water diffuses into the body of "dirty" pool water still waiting to be filtered. Regard three turnovers of your water as your minimum goal every day and if you want less exposure to chemicals or cleaner water then you can increase these numbers even further. A 20x40' pool with a 3.5' shallow end and 8' deep end might have an approximate volume of 30,000 gallons depending on the wall, floor and slope profiles. This means your 24 hour filtration goal should be in the 90,000 gallons range. Yes you can filter less. Many residential pool owners do, but if you can have the best of both worlds in more filtered water but for less cost then perhaps it is worth considering.
24 Hour filtration example
Pipe size = 1.5" PVC
TDH = 30'
Filter pressure = 10.5 PSI @ 3450 RPM
Pump = Hayward Super Pump VS (SP2603VSP)
Filtration total = 82,920 gallons
Electrical use = 18.2 kWh
24 hour cost = $2.37
The point of major efficiency loss in PVC pipes is water velocity above 6 feet per second. In 1.5" PVC this represents about 38 GPM. This means that past this point there will be a sharp increase in efficiency loss due to friction and turbulence in the pipes. Unfortunately with a large pool and small plumbing lines most, if not all of the day will need to see the pump running at higher RPM ranges. In this case the best plan is to reduce on the pump RPM just enough to experience some cost savings but not turned down so much as to limit the amount of filtered water we are getting. We still have a pretty high total daily filtration goal to ty to fit through these small 1.5" plumbing lines. Turning down the RPM of the pump below maximum speed, even by a few hundred RPM only, you can save a significant amount of power consumption with only minimal loss to flow potential.
24 Hour schedule
5am - 11am = 2500 RPM
11am - 12pm = 3450 RPM
12pm - 8pm = 2500 RPM
8pm - 2am = 3200 RPM
2am - 5am = 3450 RPM
After 24 hours we have a total of 14 hours at 2500 RPM, six hours at 3200 RPM and four hours at 3450 RPM. This provides a total of 82,920 gallons of filtered water for a total 24 hour cost of approximately $2.37 which is very lean for a pool this large. While we failed to meet the ideal filtration goal of 90,000 gallons per day we were able to achieve about 92% of this ideal goal. Best of all we were able to do so with very little electrical cost for 24 hours of pump operation. Considering a 20x40' pool with 1.5" pipes is a worst case scenario for efficiency, this is a pretty solid filtration schedule plan overall.
Filtration totals
2500 RPM (50.5 GPM) = 42,420 gallons after 14 hours
3200 RPM (65.5 GPM)= 23,580 gallons after 6 hours
3450 RPM (70.5 GPM) = 16,920 gallons after 4 hours
Total filtration = 82,920 gallons / day
Electrical consumption totals
2500 RPM (500 Watts) = 7.0kW after 14 hours
3200 RPM (1020 Watts) = 6.12kW after 6 hours
3450 RPM (1270 Watts) = 5.08kW after 4 hours
Total electrical use = 18.2 kWh / day
Total cost (18.2 x $0.13) = $2.37 / day
Having a large swimming pool and small plumbing lines is pretty much a worst case scenario from an efficiency perspective. Still, with some smart programming and a 24 hour filtration schedule (along with the Hayward Super Pump VS) we are able to filter enough water to keep this large pool in tip top water condition without breaking the bank on electrical costs to run the pump. A few hundred RPM down from maximum speed really does make a large difference to the power consumption while only minimally affecting the flow rates.
If you are lucky and have multiple 1.5" pipes on your large swimming pool then you could look at upgrading the equipment pad plumbing. If you have multiple 1.5" pipes on the suction side of your pump then it would be an advantage to you to have these pipes meet together in a 2" suction side manifold. By having multiple 1.5" lines converge at a 2" line you can reduce the water velocity and increase the efficiency of flow for a given volume of water. Since the greatest number of twists and turns (resistance to flow) happens on the equipment pad you can noticeably increase your flow efficiency by upgrading to 2" pipes throughout the equipment pad where the greatest transmission losses occur.
See this same schedule tested on the same plumbing system using 2" pipes instead of 1.5" pipes in this example: 20x40' filtration schedule (2 inch pipes)
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Swimming Pool Steve is an award winning, second generation swimming pool and spa specialist from Ontario Canada. With over 10,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the 2018 Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
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