Pressure problems

Lately I've been having filter pressures up to 30psi in a matter of days and even after I backwash 2 or 3 times, the pressure doesn't go below 20psi. It is definitely time to break down the filter and clean it but I can never get down to the 12-13psi range that I want. I wonder if the pump is just too big for the filter or whether the filter should be larger. The pump is about 27' from the main drain(horizontally). The plumbing is 2". I've read a lot lately about 2 speed pumps but don't know what size would be adequate or how you would use the 2nd speed. Thanks for any help and/or opinions. I LOVE this website!!!

Did the pressure ever get to the 12 or 13 psi you want? Was it lower when the equipment was new? If not, you may never get there. My pressure runs around 20 when everything is clean and new. The normal operating pressure depends on the pump size, filter state, pipe size and length of run, number and size of return openings, etc.

You could try using a larger size return fitting if available (go from a 1/2" opening to a 1", for examaple) if you really need the pressure to be lower and everything else about the system is okay.

You didn't say what kind of filter you have so this may or may not apply. I have a DE filter. When the pool was new and I was going through the initial plaster curing/brushing the pressure went up to 30. I tried backflushing it several times but it only lowered the pressure (to 20) for a day or so then it would climb back to 30. I ended up disassembling the filter and repalceing the DE powder to correct. The old DE powder was cacked with plaster dust and backwashing would not clear it. With new powder in place I'm on the 4th or 5th month without needing to clean or backflush.

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Originally Posted by Sumo1

Lately I've been having filter pressures up to 30psi in a matter of days and even after I backwash 2 or 3 times, the pressure doesn't go below 20psi. It is definitely time to break down the filter and clean it but I can never get down to the 12-13psi range that I want. I wonder if the pump is just too big for the filter or whether the filter should be larger. The pump is about 27' from the main drain(horizontally). The plumbing is 2". I've read a lot lately about 2 speed pumps but don't know what size would be adequate or how you would use the 2nd speed. Thanks for any help and/or opinions. I LOVE this website!!!

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The 2 HP pump is oversized for general circulation but you need it for the spa jets. A 2 speed pump would probably be the easiest change to make. You can use low speed for general filtering and circulation and high speed for the the spa jets.

My guess is you are running at least 60 feet of head when clean and over 75 feet of head when dirty. A 2 HP high efficiency pump should deliver about 110 GPM at 60' which would be about 4 hours of turnover. A two speed pump 2 HP on low speed would be about 8 hour turnover which is perfect for your pool.

Also, Is there a reason the filter gets dirty so quickly? Is it a new plaster pool?

Thanks for the response. I've lived here for 4 years. I believe it was built in 1985. I neglected to mention that there is a Tropic Air 1hp pump that blows air through the spa jets. I have 2 skimmers, one about 20' from the pump and the other at the far end of the pool. The far skimmer doesn't draw very well so I've had it plugged all summer. I bought new DE grids 2-2 1/2 years ago. I can only remember seeing pressure as low as 12-13 maybe once or twice since I've been at this. Since I've got all these various pumps, perhaps I could downsize the main to 3/4 or so?????? I usually run the system about 10hrs a day. I would love to reduce my pool related power consumption. There's also a pool furnace but we haven't used it in 2 years. Ideas??

Just saw your PM, sorry I did not respond earlier. I don't know if you solved your problem but a couple of observations:

I am not an expert on DE filters so I cannot offer much help there. However, if there is a way to operate the filter without the grids, you can check if the pressure is coming from the grids or not. If not, then you can look other places.

A couple rules of thumb regarding pressure and suction:

Low pressure readings can mean low restrictions on the pressure side (good thing) or high restrictions on suction side (not a good thing).

High pressure readings can mean low restrictions on the suction side (good thing) or high restrictions on pressure side (not a good thing).

Point is you cannot tell from the pressure reading alone if you have a problem or not. Valve settings will have an effect on filter pressure so try different settings to see if the pressure you noticed before was due to a particular configuration:
Pool Mode
Spa Mode
Spill over Mode

As I mentioned before, your turnover is currently about 4 hours. Most you would need would be 8 hours during the peak of the summer. Any reason you are running the pump 10 hours?

Blowers do not make up for low HP pumps so you do not want to lower the HP of the pump unless you plan on having a separate pump for the jets. So your options are:

1) 2 Speed 2 HP pump replacement. Reduce your power bill by 69% with 8 hour run time at low speed.
2) 2 x 1 speed pumps. Re plumb 2 HP pump for Spa Jets only and purchase a 3/4 HP pump and plumb from for pool only. Reduce your power bill by 67% with 6 hour run time.
3) Reduce pump run time for current configuration. Reduce your power bill by 20%.

Thanks, Mark. I'm certainly not an expert on DE filters but I like the results of using one and I'm learning. I will play around with the valve settings this weekend and report back soon. This may seem a needless question but I need a clarification--when you say 'suction side' does that mean the intake side up to the pump itself? Does 'pressure side' include the filter? Regarding the options you listed, I like adding a 3/4 pump best because I find nothing wrong with the 2hp. Have a good weekend! Hal

Suction side is from your skimmer/main drain to the pump. Pressure side is from the pump through the filter, heater, valves, etc out the returns.

One thing to be aware of is that the 3/4 HP pump option will require some additional plumbing so the spa can share the filter and heater while still maintaining separate pumps, assuming you don't have two suction and return lines for the spa. You will need additional valves and lockout protection so that the pumps cannot run dry. There might be other creative ways to plumb both pumps to minimize the rework. Do you plan on doing this yourself?

By the time you add the extra valves required for option 2, you may find that option 1 is actually cheaper and much less work. Also, you might be able to sell your old pump on Ebay or Craigslist :-).

Valve settings will have an effect on filter pressure so try different settings to see if the pressure you noticed before was due to a particular configuration:
Pool Mode
Spa Mode
Spill over Mode

As I mentioned before, your turnover is currently about 4 hours. Most you would need would be 8 hours during the peak of the summer. Any reason you are running the pump 10 hours?


1) 2 Speed 2 HP pump replacement. Reduce your power bill by 69% with 8 hour run time at low speed.
2) 2 x 1 speed pumps. Re plumb 2 HP pump for Spa Jets only and purchase a 3/4 HP pump and plumb from for pool only. Reduce your power bill by 67% with 6 hour run time.
3) Reduce pump run time for current configuration. Reduce your power bill by 20%.[/QUOTE]


--Sorry, I don't know how to highlight your quote--
I ran the pump 10 hrs/day based, I guess, on the man I bought the house from. I believe that's what he told me, though he may have been guessing just like me. That was before I found this website and discovered there are calculators to estimate pool volume and water flow and such as that. Concerning adjusting valves to influence filter pressure, I spent some time playing with the system and got the following indicated pressures: Main drain only-25psi Main drain50%skimmer50%-30psi Skimmer only-30psi Can't recall whether I pulled from the spa but that's something I rarely do. I usually just return about 40% through the spa to keep it flushed out. I don't have the waterfall type. Anyway, it seems I may have a blockage in the skimmer line. I'm afraid I'd have to cut the intake manifold to blow back through the skimmer.... Wonder if there's a way to pull the stuff back out through the skimmer?TIA :) Hal

I know it is counter intuitive but if your pressure goes up with the skimmer only, it means that there is less restriction via the skimmer and not more. Pressure is measured on the return side not the suction so it reads as the opposite for the suction side.

It is typical in a pool to have the main drain have more restriction than the skimmer since it is a longer run and usually smaller pipe so you may be ok there. Before you cut any pipe, I would make sure you acutally have a problem. From what you have said, everything sounds normal to me.

You will not get the PSI down to 12 unless you change your pump to a lower HP. Larger HP means higher PSI. I hyave a 1 HP motor and my pressure is about 20 PSI so I think this is probably normal for you.

Also, it sounds as though you may be cleaning something out of the pool since it raises from 20 PSI to 30 PSI in a short period of time.