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Thread: Sand filter PSI dropped from ~22 to ~8 during SLAM?

  1. Back To Top    #1

    Join Date
    Mar 2015

    Sand filter PSI dropped from ~22 to ~8 during SLAM?

    I am in the middle of a SLAM. The PSI gauge on my Hayward sand filter has been slowly creeping up over the last few weeks, and even after a backwash does not go down. And it doesnt go down when the pump is off either, so I figure its either broken or malfunctioning. However, I went out yesterday to brush the pool and add bleach, and saw that the PSI was 8. It had been around 22 earlier in the day. Since the gauge is suspect, Im not sure whats really going on. However, I went and checked the flow at the return jets into the pool and they are definitely flowing stronger than normal.

    So now Im wondering if somehow the filter is somehow being bypassed since the pressure is so low. Is this possible? The selector is in the normal 'Filter' position. Can a Hayward sand filter malfunction in this way?

    One more piece of info, I added about a cup of DE mixed with water to the skimmer the day before this to help clean up the water during the SLAM.

    I ordered a new glycerine filled PSI gauge from tf, but dont have it yet.

    Thanks for any help!
    18,000 Gallon in ground pool with SWG
    Plaster surface, Maytronics Z5 robot
    Multi speed pump, Hayward sand filter
    TF-100 test kit
    K-1766 salt test kit

  2. Back To Top    #2
    Mod Squad
    Join Date
    Aug 2012
    DFW, TX

    Re: Sand filter PSI dropped from ~22 to ~8 during SLAM?

    I would wait for the pressure gauge and go from there. The readings from your broken gauge are as suspect as test strips and pool store test results!
    TFP Moderator
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

  3. Back To Top    #3
    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Sand filter PSI dropped from ~22 to ~8 during SLAM?

    Your spider gasket might have torn which is allowing water to bypass the filter (low pressure in tank) and return directly to the pool (higher flow)
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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