Greetings, I've been scouring the web about variable speed pumps, as I will be replacing all of our pool equipment during a complete remodel that will begin later this week. I understand the cost saving that a variable speed pump provides, but we seem to have lower electrical costs in my area, so the pay-back might be drawn out. Also, nearly every time I read about folks using variable speed pumps, they're on pools with water features, heaters, floor cleaning systems, etc. Our pool is very basic: 1.5" plumbing Separate skimmer, main drain and cleaner suction lines 3 returns Will the investment in a variable speed pump pay off in my case? Two speed pumps are an option, but an expensive timer is required unless you switch manually, and I'll need to do something in order for the pool cleaner to work. Or, do I just get one of the more energy efficient, single speed pumps? Thanks!

Chlorine, when energized, escapes the water and enters the atmosphere. This is off gassing. UV light from the sun will energize it. Cyanuric acid, aka CYA or stabilizer keeps the chlorine sort of busy so even if it does get some energy from the UV, it isn't enough to keep it from "playing" with the CYA in the water.This also can keep it from doing work though so having too much CYA prevents Free Chlorine. aka FC, from doing it's jobs of oxidation and killing biological pathogens. Generally speaking, you need about 5 to 7% of the ppm count of CYA for FC with salt cell equipped pools and 8 to 10% for all other forms of feeding chlorine to a pool. Too much CYA, and the elevated levels of FC are very difficult to make happen on a regular basis. If the CYA were 150 ppm, can you see trying to maintain a residual of 12 to 15 ppm? Drop the CYA to 30 ppm and 2 ppm of FC is much easier and costs less. Please note that salt cell equipped pools often have somewhat higher levels of CYA and FC to reduce the cell's ON time so it lasts longer. Generally, pools, when on, they either have a tablet feeder or tabs in the skimmer (generally not a good idea, BTW) or a salt cell which won't work without water moving. Pools get the most use during the day. Activity will cause some gas off too, in addition to the demands that sweat, tanning lotions, killing bio-badies, etc... place on the residual FC in the pool. These can deplete a pool pretty quickly if the FC isn't replenished as it's being used. You need to keep that residual FC in there. Running at night when nobody is there doesn't help the swimmers if it isn't there when they are. Without the UV of the sun, aka night, the FC stays put. The water is safe. I do recommend keeping the pump running whenever there are swimmers using the pool, day or night. Scott

Personally, I would not trust any tool from a manufacture that is trying to sell you a pump. That is why I developed my own spreadsheet using the data published by the California Energy Commission. The manufacture tools generally use gross approximations and tend to use unrealistic scenarios plus they don't show you how the calculations are done. You can download the CEC data yourself or you can download the spreadsheet below and do the analysis yourself. Unlike the manufactures web site tools, I built a completely transparent tool open for full review so I am not trying to hide anything from the user. But it really only takes simple math to prove the case of a two speed pump in some situations. Assuming decent plumbing and using the CEC data from Curve-C, a Whisperflo WFDS-24 will produce about 42 GPM @ 380 watts while an Intelliflo will produce about 30 GPM @ 140 watts for a difference of 240 watts. This may seem like a big difference but the money saved is not all that great. In a 15k pool and a turnover per day, the Whisperflo requires 357 minutes on low speed while the Inteliflo requires 500 minutes for the same turnover. So the Whisperflo uses 2.3 kwh/day and the Inteliflo uses 1.2 kwh/day or a difference of 1.1 kwh/day. Again, it sounds big until you apply the electrical rates. So if your electricity rate is $0.07/kwh to make up the $500 cost difference between the two pumps you would need about 6500 days (>200 months) of run time before the Intelliflo starts to be more cost effective than the Whisperflo. However, you can make the case for the Intelliflo by changing some of the assumptions. For example, if the electrical rate is $0.30 like in CA and the user was running two turnovers per day, then the Intelliflo will become more cost effective than the Whisperflo after only 750 days (25 months) which makes the Intelliflo the better choice. However, some POs need to run their pumps at higher speeds for part of the day to run cleaners and/or solar so that can diminish some of the benefit. Even though we have high electricity rates here in CA, I chose the two speed because much of time I run the pump at higher speeds for solar so the benefit of the VS was not as great for me. You can see my situation in Scenario 3 of the spreadsheet. I modified a 1 HP Northstar pump to create a 1/2 HP two speed pump but was able to do that for only $120 so it would be hard for any pump to beat that lifetime cost. Anyway, you can run all of these different scenarios using the spreadsheet. Here is a link that might be useful: Pump Cost Calculator

You have anther post about a negative edge design. If this is the same builder, and he recommends a singe pump design for a pool with a negative edge, thank him and send him on his way. I find it hard to believe he has designed others successfully. He also hasn't been educated to understand how beneficial two seed and variable speeds are when it comes t energy savings. If he has been, what else has he been less than forthcoming with? The pool filter system should be separated from the negative edge. The pool filter system can run a spa but not a spa and the negative edge at the same time. Most negative edges are visible in the yard and looking pretty is important. Negative edges typically need between 10 and 20 gallons per foot,, depending on the back side of the edge and the effect desired. Spilling straight down does not require the same amount of water as a sheer arcing away from the wall. Negative edges should be driven by their own pump. Which pump to use here will be dictated by the edges design parameters. For the pool, we need more information about the design. How many spa jets, plumbing size, how dar away will the equipment be, and any other details you can think of will help us to help you. Scott