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Thread: PSI reading is consistently high?

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    PSI reading is consistently high?

    Since we had our pool opened a month ago, our PSI has been reading around 26 consistently. Backwashing for 3 minutes a time does not change the reading. The water in the sight glass is definitely clear at the end of backwash. I thought it was the gauge which we replaced yesterday, but the new one shows the same reading and the gaue does go to 0 when the pump is off. The sand in the filter was replaced last summer. Any ideas?
    18x36 ft
    19,000 gal IG vinyl
    Sand filter Tagelus 24"
    1HP Whisper Flo Pump

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    Mod Squad JohnT's Avatar
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    Re: PSI reading is consistently high?

    A couple of guesses: Eyeballs not rotated properly. Caps not removed from some returns.

    How does the water flow feel at each return?
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    20K Gallon 20X36 Vinyl Inground
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    Re: PSI reading is consistently high?

    All the caps have been removed. Currently the returns are pointed up because we are trying to get the TA down with muratic acid and bringing PH up with aeration. The returns were straight down prior to that with the same PSI reading. The pressure is very good coming from all of the returns, there are 6 total. There is also a main drain and 3 in-floor pop-up valves.
    18x36 ft
    19,000 gal IG vinyl
    Sand filter Tagelus 24"
    1HP Whisper Flo Pump

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    Re: PSI reading is consistently high?

    what was your psi when you closed last year?
    Dave S. - Forum owner
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    Mod Squad JohnT's Avatar
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    Re: PSI reading is consistently high?

    Set your multiport to recirculate and see what the pressure does.
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    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: PSI reading is consistently high?

    Unfortunately I don't know what the pressure was at closing. We have the service department from the pool builder close and open the pool for us. Honestly I was just doing what they said to do which was backwash every week, not really even paying attention to the PSI reading. I hadn't found this site yet! When the multivalve port is in recirculate the PSI reading is still 26, no change.
    18x36 ft
    19,000 gal IG vinyl
    Sand filter Tagelus 24"
    1HP Whisper Flo Pump

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    Re: PSI reading is consistently high?

    jm,

    Well, 26 is a little high but it may be normal for your pool....although I doubt it.

    High pressure results from some type of restriction after the pump. Dirty filter is the most common and backwashing eliminates that. Since that's not your issue, you need to examine each portion of your system from the pump to where the water reenters the pool. You may have a valve 1/2 closed, etc. but there is probably a restriction somewhere. If you can find nothing, then I think you can assume that's your normal psi.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: PSI reading is consistently high?

    Did I understand correctly that you have an in floor cleaning system? In floor cleaning systems often require comparatively high pressure.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: PSI reading is consistently high?

    We do have an in floor cleaning system with 3 pop up valves. If this pressure is "normal" for our pool, how do I know at which point the filter needs to be backwashed? Is it a good idea to backwash on a weekly basis with a sand filter?
    18x36 ft
    19,000 gal IG vinyl
    Sand filter Tagelus 24"
    1HP Whisper Flo Pump

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    JasonLion's Avatar
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    Re: PSI reading is consistently high?

    You backwash the filter when the pressure goes up about 6 PSI from the filter clean pressure, so around 32 PSI.

    There is no need to backwash weekly. Watch the pressure gauge, it might be more often then weekly, or (much more likely) less often than weekly.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: PSI reading is consistently high?

    If this pressure is "normal" for our pool, how do I know at which point the filter needs to be backwashed?
    As your filter collects dirt, the pressure will increase. Many folks say backwash with an increase of 6-8 psi and that certainly works. I like to think in terms of a percentage increase......say 30% or so.

    So, if your system normally runs at 10psi, you would backwash @ 13-14 psi.

    Since your system may be normal @ 26psi (I still have reservations about that) you would backwash @ 33psi or so.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: PSI reading is consistently high?

    Does the distance from the equipment to the pool have anything to do with the pressure?
    18x36 ft
    19,000 gal IG vinyl
    Sand filter Tagelus 24"
    1HP Whisper Flo Pump

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    Re: PSI reading is consistently high?

    Not in a significant way.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: PSI reading is consistently high?

    If you have 1 1/2" plumbing then this might be about right for the pressure but it depends on the suction side plumbing as well. If the suction side is larger pipe or has multiple runs, then it is pretty easy to get to 26 PSI. Can you describe the pipe diameter, number of runs pool to pad for suction and return and also their lengths?
    Mark
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    Re: PSI reading is consistently high?

    Ok here goes...Suction side is the main drain and 1 skimmer, both pipes are 2" and run approximately 50 ft from pool to pad. Returns pipes are 1.5" using a Paramount in-floor cleaning system cycling between 6 pipes. Approximately 45 ft from pool to unit. Paramount valve reading is 5 PSI. Does this make sense?!
    18x36 ft
    19,000 gal IG vinyl
    Sand filter Tagelus 24"
    1HP Whisper Flo Pump

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    Re: PSI reading is consistently high?

    Using just the numbers you gave me, my head loss model predicts 25.9 PSI with a total head loss of 66 feet and 69 GPM. I am assuming that the floor cleaner is running and only one of the 6 pipes is operating at a time. So I think the pressure you are seeing is reasonable for your setup.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner

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    Re: PSI reading is consistently high?

    I didn't totally understand everything you said but it is good to know that number is reasonable! Now I will just watch for it to go up to 32-33 PSI before backwashing. Thank you so much for your expertise.
    18x36 ft
    19,000 gal IG vinyl
    Sand filter Tagelus 24"
    1HP Whisper Flo Pump

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    Re: PSI reading is consistently high?

    Quote Originally Posted by jmlodin
    I didn't totally understand everything you said but it is good to know that number is reasonable! Now I will just watch for it to go up to 32-33 PSI before backwashing. Thank you so much for your expertise.
    Sorry about that. Let me explain a little more. Using the pipe diameter, pipe lengths, filter PSI, pool pump head curve and a few other esitmates, I can predict with some accuracy what the operating point (i.e. GPM and head loss) is for a particular pool/plumbing combo. With your setup, the pump is probably delivering close to 69 GPM with a clean filter.

    However, if you wait until 32 PSI, the pump will be delivering only about 45 GPM. This will increase the turnover time by 50% or for the same pump run time, it will decrease the amount of water being filtered by 35% so it is something to keep in mind.

    A dirty filter might filter better but because of the increase in pressue, the pump won't filter as much water either. Also, running at a higher filter pressure means that the in-floor head pressure and flow rate will be lower so they may not work as well.

    Given your situation, it might be better to clean the filter before reaching 30 PSI but it depends on your schedule and how often you are willing to clean the filter. Hopefully with a sand filter, backwashing a bit more often shouldn't be too much of a burden but it is entirely up to you.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner

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    Re: PSI reading is consistently high?

    Thanks for the clarification. I will watch the gauge and backwash before it hits 30. I don't mind backwashing. I was doing it on a weekly basis according to the pool builders/store instructions. I was also doing a lot of other "mindless" tasks according to their instructions that I will no longer be doing!
    18x36 ft
    19,000 gal IG vinyl
    Sand filter Tagelus 24"
    1HP Whisper Flo Pump

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