Pump Pressure

[rilesworld]

I have a Hayward S200 sand filter and a 1.5hp (I think) pump that operates clean at 26psi and I let it get up above 30psi before I backwash. Is that operating pressure too high?

I have an inground pool, 20,000 gallons with two returns and two intakes. One intake is at the skimmer basket and the other intake looks like it may have been for a suction side cleaner. I typically keep this one plugged because I don't have suction side cleaner and it is installed rather close to the surface so when the water level drops it seems like I would get air in this intake.

Is my thinking OK here?

[nater]

My initial reaction is that your pump is oversized for your pool (a common mistake by pool builders). I have the same filter and a 3/4 HP hayward pump in a 19,000 gallon pool with similar returns. My filter pressure is about 13 psi just after a backwash.

Of course, your pressure will depend on piping size, length, number of fittings and elbows, water features, etc but that sounds pretty high. Double check the name plate on your pump for the model# and rated HP.

Do you find a lot of sand in the pool? That would indicate the pump is overpowering the filter and water is "channeling" through the filter bed and carrying some sand back to the pool. If not, and your water stays clean, worst case is that your electric bill is higher than it should be.

Some of the experts like CarlD or Waste may have some additional thoughts...

[rilesworld]

Thanks, I will double check the pump size when I get home this afternoon.

This is my first year with the pool and we have just been getting it cleaned up. Silt does appear on the bottom after I vacuum, but I was assuming that it was just silt that I stirred up during my cleaning that just settled back down, rather than coming from the filter. I guess I could try the panty hose trick over a return to see if any silt is coming through the returns.

Is there any harm in operating at this pressure? I doubt I would replace it just to prevent some silt from channeling through unless there were some other reason.

I was also thinking of using some DE in my sand filter as suggested on this forum, but this would raise my pressure even more. Is that a bad idea?

Thanks.

[rilesworld]

I checked this morning, and my pump is actually a 1hp pump. I'm not sure if that changes anything.

Thanks.

[mas985]

What is the service factor? A pump's true braking HP is really the labeled HP times the service factor.

Also, high pressure could also mean small pipes. What is the diameter of your pipes?

[Sardian]

Also, check to see what your pressure is with the pump turned OFF. If there is any water at all left in the pressure guage over the winter, it will freeze and mess up the reading of the guage.

With the pump turned OFF you should get a pressure reading of ZERO. If it is anything other then you need to subtract this from your pressure reading to get your actual pressure. If this is the case, the guages aren't hard to replace.

[rilesworld]

My pipes are 1.5" diameter pipes and my service factor is 1.5.

I'm not sure what the service factor tells me though??

As the above poster suggested, I think it may be a bad pressure gauge. It seems to only drop down to about 12psi when I turn the pump off and I can tap on the glass and appears to stick quite a bit. Hopefully this is easy to replace?

Thanks for the help.

Jeff

[Watermom]

Yes, and also cheap to replace.

[catnip]

You might try a quick temporary fix for your sticking gauge (worked for me at least). Unscrew it and give the inlet fitting a good rap on something solid. In my case it dislodged some rust and moisture and the gauge went down to zero; this "might" get you by until you can get a replacement.

BTW, I just looked on Grainger's web site and you can get an all stainless (all metal parts) liquid-filled 2.5", 60 psi gauge for $25.25 plus shipping. The cheap ones (10 bucks) from the pool store seem to last about a year before suffering from corrosion. I'm about to order one to see how long it holds up.

You might also look up the pump curve for your pump on the manufacturer's web site (some e-tailers also post the curves) and see what kind of flow you should be getting with the pressure you are showing. You will need to calculate the total dynamic head (TDH) in feet as input to the pump curve which consists of the pressure head which is the pressure in psi you are seeing on your filter gauge X 2.31 (ignoring the pressure loss from the pump to the filter) plus the suction head from the drains/skimmers to the pump which you can guesstimate as 5-10 feet, i.e.

TDH = (Filter Pressure x 2.31) + Estimated Suction Head

For your clean filter pressure of 26 psi and estimating 8 feet of suction head that would equate to:

TDH = (26 x 2.31) + 8 = 68 ft.

At 30 psi the TDH is 77 ft. This is a pretty high head for most pumps but not unmanageable for some. In any case with 1.5 inch return plumbing you want to keep the flow under 63 GPM which is based upon a maximum flow rate of 10 feet per second. However, the Hayward spec on the S200 filter shows a design flow rate of 44 GPM, so you really want to stay around or slightly below that rate. My guess is that your pump is over-sized for your filter and 1.5" plumbing and is attempting to push too much water which results in the higher pressures you are seeing. If this is true, you could save money on electricity and have a more "efficient/balanced" overall system with a smaller pump (3/4 or perhaps even 1/2 HP full rated).

Here is a link to pump/filter sizing guide on Hayward's site:
http://www.haywardnet.com/pdfs/Pump_filter_sizing.pdf