Correct Pump/Filter?

[cpmart]

Hello

We moved into a house with an inground pool about 3 years ago, and the BBB method has been working great for us for the past year and a half (after doing baquacil and the pool store thing the first season and a half). Now that the water quality seems to be running smoothly (thanks for the help, guys) we are looking more carefully at the hardware.

After getting yet another high electric bill, I started wondering if our pump-filter-pool were correctly sized for each other, and if a smaller pump might be in order (or a 2 speed pump) to improve our filtering and save us on our electric bill too. I have read through some of the pump threads, but am still unclear if our setup is ok...I am thinking something is mis-sized.

Here's what we got:

24,000 gallon inground pool (2 returns, 1 skimmer, 1 main drain)
Sand filter (Hayward model S210T, 200lb sand, 44 gpm "design flow rate" and 10 hr turnover rate of 26,400 gal...spec from website)
Pump (Hayward Superpump model 261X15, 1 1/2 horsepower, 50-67 gpm output at an estimated head of 50 to 60 feet, so I calculate this would turn over my pool in 8 hours)

Are these things correctly matched? I read somewhere that the sand filter rate should be 25% higher than the pump rate, and that is not the case with ours (44 gpm sand filter vs. 50-67gpm pump rate). So are we getting less than optimal filtering because the pump is pushing water too quickly through the sand?

Visually, our pool looks good, and we run at a filter pressure of 10psi, but I'm wondering if we could do with a smaller pump, and if the purchase cost would be offset by electric bill savings. We usually run the pump about 12 hours a day, with an electric cost of $0.15/kwh, I get a thumbnail cost of $54/month [(11 volts*8.695 amps/1000)* hours running]. I'm going to double check this calculation at the electric meter.

Sorry for the long post, but I wanted to include all the information, and I might have gone overboard :)
Thanks in advance for any insight.
Chris

[duraleigh]

Hi, Chris,

Your numbers make sense to me.

Your pump is a little too big for that filter. To get things in balance, you could get a larger filter or a smaller pump. I have had great personal success with an oversized filter so that would be my choice. If you downsize your pump down to about 35gpm or so, you'll match well with your filter but your turnover rate will be around 12 hours....still okay, but sort of on the borderline for a nicely operating system.

After saying all that, I'm a little puzzled with your 10psi filter pressure.(are you pulling water from both the skimmer and the main drain?) That's pretty low and indicates very little resistance. (i.e. you are not overdriving your filter at 10 psi) So, I guess where I am ending up is, if that filter psi is correct, I might just leave everything alone......especially since you have no water quality issues.

[mas985]

Assuming your filter guage is correct, with a filter presure of 10 PSI, I suspect you actually have a head loss of much less than you think. Return loss is 23 feet and suction loss usually does not exceed 15 feet so you may be closer to 40 or 45 feet at the most. So your flow may be closer to 80 GPM.

You said the filter design rate is 44 GPM but is that the maximum recommended rate? If so, then you may have a concern.

[cpmart]

Dave S. The 10 psi is what it usually reads, and we usually have the valve on like 80% skimmer and 20% main drain...

My husband and I are both pool newbies, so we *think* the filtering is good, but have nothing to compare it to! We have stuff floating on the top in the am before we turn on the pump, and most of it gets swept into the skimmer, and our pool hasn't had an algae bloom all summer (thanks BBB). We have debris that always collects in certain spots (the bottom corners), and our main drain doesn't seem to do much collecting, but the pool isn't green, so we think it is working ok... :)

Mark S. I got that 44 gpm figure from the hayward website and they called it "design flow rate" The info I got off the side of our filter says "Backwash rate 44 gpm" "Max psi 50" and "Rate 20 gpm/ft^2" and "Filter area 2.2 ft ^2" The filter gauge has always read around 10-12 psi (for the last couple of years), even if we switch to all skimmer or all main drain.

I just used the estimate for head calculation of 50-60 for and inground pool...forgive my ignorance, but does that mean something is out of whack if our actual head is different than the usual head value? Thanks for the responses...

Chris

EDIT: I actually went out in the dark with a tape measure...the distance from the skimmer/main drain to the pump is 46 feet...great guess Mark!

[mas985]

There is nothing wrong with low head loss just somewhat unusual. Most pools are between 45-65 feet of head. I would say you are probably on the lower end of that scale if not below.

However, Dave could be correct that there is a restriction on the suction side but you would normally see this as air in the pump lid.

Another concern could be a damaged pump impeller. This will also show up as low PSI since the pump is not moving enough water.

Otherwise, a few things that might account for the low PSI reading: No heater, large pipes and/or short distance from pool to pad. What size is your piping?

One other thing distance is not a direct conversion to head loss so the 46 feet is a coincidence.