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Thread: DE Filter Pressure Down From 11 to 6 psi

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    Join Date
    Jul 2014
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    Billerica MA
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    DE Filter Pressure Down From 11 to 6 psi

    Hello all,

    I am hoping someone can help me figure out why my DE filter pressure has fallen from 11 psi to 6 psi this week. I have not backwashed yet since opening and I would have expected a higher pressure. I have a 20K gallon gunite pool with Hayward pump and one return line leaving the skimmer. I have excellent water pressure leaving all of my jets, my skimmer has excellent suction, there is no air in the pump basket, I cleaned the pump basket that was full of pine needles, there was a little bit of air in the filter when I opened the pressure release valve.

    I have just registered with this site, but have been following the GREAT information here since last season. This site has saved me from costly mistakes. I just bought my house with the pool in 2011 and only knew what the pool store told me. Needless to say, I always had algae appear, even when my chlorine levels were normal(which they weren't as later discovered). After reading the information here I have successfully lowered my CYA from well over 100 to 60 last season using higher chlorine levels and this season down to 25 CYA using lower chlorine levels. I discontinued using the Leslies pucks with CYA built in and only use sodium hypochlorite now. I never had an algae siting again after using the chemical guidelines used here.

    Free Chlorine: 3.5 ppm
    CC: 0 ppm
    PH: 7.4
    Alk: 100
    CH: 190
    CYA 25 (might even be less)

    Thanks

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,879

    Re: DE Filter Pressure Down From 11 to 6 psi

    Welcome to TFP!

    There are a couple of possibilities. A broken pressure gauge. A partial blockage or closed valve on the suction side of the pump would lower the pressure on the filter side. Opening a valve on the pressure side that had been closed previously. A major leak in the pressure side plumbing.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Richard320's Avatar
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    Jan 2010
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    San Dimas, CA (LA County)
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    18,768

    Re: DE Filter Pressure Down From 11 to 6 psi

    Pine needles in the basket makes me think there may be pine needles in the impeller, too. They can slip right through the strainer basket if they hit at the right angle.
    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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    Join Date
    Jul 2014
    Location
    Billerica MA
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    Re: DE Filter Pressure Down From 11 to 6 psi

    Thank you both. Pressure gauge is doubtful, it does go to zero easily when I shut down the pump. Can't be a major leak because my water level in the pool is exactly the same for the past few days with pump running 10 plus hours daily. Not sure how there could be a blockage with the excellent flow I have. No valves have been opened or closed. So I guess it sounds like it would either be the pressure gauge or the impeller having pine needles. The pump basket was loaded with them when I emptied it. One other thing I noticed today is that I released the air from the filter pressure release valve this morning(I had to prime the pump yesterday after emptying the basket) and this afternoon I opened the pressure release valve to see if any air was in the filter and I heard the air coming out for a good 2-3 seconds. The pump was on all day. First, how could I be getting air in the filter when I see absolutely no air bubbles in the pump basket, could that be causing the low pressure? Second, how would pine needles stuck in the impeller lower the pressure but have no effect on the return jet pressure? It could just be me, but I thought the pump sounded a little bit louder than normal(it is 1 1/2 HP SF of 1)Hayward Super Pump two years old. Could I ruin the pump if I don't fix the unknown issue or clean out the needles? I will have to learn how to gain access to the impeller if necessary.

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    Join Date
    Jul 2014
    Location
    Billerica MA
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    4

    Re: DE Filter Pressure Down From 11 to 6 psi

    Problem Solved!!!
    I shut down the pump, opened the air relief on the filter, took the pump basket out and felt inside the impeller for debris. It was loaded with pine needles! I cleaned them all out thoroughly and put everything back together. Primed the pump and the pressure is back up to 11, the pump sounds much better and the pressure out of the return jets is much more powerful. I didn't realize how much pressure they had lost. I can't thank you enough for the advice! I have added a skimmer basket sock to collect pine needles in the future.
    I clearly had lost return jet pressure and did not have excellent flow as I previously thought.
    Thanks for the help!
    20K gallon, plaster, Hayward Super Pump 1 1/2 HP, DE Micro Filter 36 Sq Ft/72GPM, Dolphin cleaning robot, in-line chorine feeder(no longer used since finding TFP)

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