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Thread: low flow from filter/high psi

  1. Back To Top    #1

    Join Date
    Aug 2016
    Hendersonville nc

    low flow from filter/high psi

    we are at our wits end.We have a new 24' above ground pool.
    It was installed last august and all was fine. We closed the pool and just opened it about 2 weeks ago.
    We did all the recommended steps. The initial psi about 12-15. output flow was strong. Then the next morning
    we noticed the flow was very weak and the psi 20.
    We completely cleaned the pump and impellers. We removed the sand from the filter cleaned everything and replaced it with new #20 silica sand.
    We back washed, rinsed and restarted the system. Psi again about 15. and STRONG flow from the output. After about 4 hours
    again the psi were about 20 and the flow almost nothing. We have redone everything several times all with the same results.
    We are frustrated and don't know what to do.
    24' above ground pool 17000 gal.
    hayward pro series high rate sand filter
    hayward power matrix pump

  2. Back To Top    #2
    Mod Squad woodyp's Avatar
    Join Date
    Apr 2010
    East Texas

    Re: low flow from filter/high psi

    Welcome to the forum. Gotta ask..................does the pool have green algae in it. Full of leaves or pollen? Is the water clear? No need to change the sand btw.
    Got any GOOD test results for us?
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  3. Back To Top    #3
    Mod Squad Jimrahbe's Avatar
    Join Date
    Jul 2014
    Bedford, TX

    Re: low flow from filter/high psi


    Welcome to TFP.. A Great resource for all your pool questions.

    You might not know what to do, but your filter does...

    Your filter is doing what it should by capturing all the dead junk in your pool.

    There is almost never a reason to replace the sand, just backwash and rinse and repeat.

    My guess is that your water is either green or very cloudy. This is an indication that you have algae and that is what is clogging your filter.

    Assuming I am right about your water color, you will need to perform a SLAM... See this ....

    To perform the SLAM, you will need one of two test kits... either the TF-100 or the Taylor K2006C...

    Here is another pretty good read....

    Thanks for posting,
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  4. Back To Top    #4

    Join Date
    Aug 2016
    Hendersonville nc

    Re: low flow from filter/high psi green algae water is clear
    no leaves or pollen
    one thing I forgot to post is that when we put the filter on recirculate the flow is strong.
    not sure what you mean by good test results. We have done everything we can think of.
    when the flow is weak if we turn the pump off and then on again everything works good. PSI 15 and strong output. then after a few hours psi 20 and almost nothing from the return line....

    - - - Updated - - -

    no green water. Its clear and all numbers are correct. I was a chemistry major in college....
    We have the good test kit also....
    24' above ground pool 17000 gal.
    hayward pro series high rate sand filter
    hayward power matrix pump

  5. Back To Top    #5
    CJadamec's Avatar
    Join Date
    Apr 2016
    Quaker Hill, CT

    Re: low flow from filter/high psi

    When you recirculate you are bypassing the sand bed and not filtering the water. Like the others have said it sounds like your filter is doing its job and removing things from the water. If you do a backwash and rinse and the return goes back to normal then the filter is working and there is something in your water the filter is taking out. The water doesn't have to be green or cloudy for there to be an algae bloom in your pool that would clog the filter, but when we say clear we mean crystal clear to the point where you can see every little spec of sand on the bottom of the pool when looking at it from the deck.

    By good test results we are looking for a run down of the pH, Free chlorine (FC), Combined Chloramines (CC an indicator of oxidized chlorine and presence of algae), Cyuranic acid (CYA), total alkalinity (TA) and calcium hardness (CH). If your test kits provides you will all these readings we would consider it a good test kit.

    99 times out of 100 there is nothing wrong with your sand filter they are very simple things and don't fail often.
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  6. Back To Top    #6
    mas985's Avatar
    Join Date
    May 2007
    Pleasanton, CA

    Re: low flow from filter/high psi

    After you backwash the filter, does the pressure go back down?

    Do you have any FC loss overnight?
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