Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 6 of 6

Thread: Sand filter pressure rises with use then returns to clean pressure with OFF/ON cycle?

  1. Back To Top    #1
    gtemkin's Avatar
    Join Date
    Jun 2008
    Location
    Seattle, WA
    Posts
    738

    Sand filter pressure rises with use then returns to clean pressure with OFF/ON cycle?

    My sand filter has had odd behavior that I wondered if anyone else has seen.

    The gauge goes to zero when off and is around 10psi when the pump is on and the sand is clean. If I run my suction side Kreepy Krauley after not having cleaned the pool for a week or so (there's small leaves on the bottom and maybe some unseen fine silt or dirt down there) after a few hours the gauge gradually climbs to around 15 and the Kreepy Krauley slows somewhat. So far, that's perfectly normal behavior for my equipment and I would then normally perform a backwash. However, if I don't backwash and instead, just shut off the pump and then turn it back on, the filter pressure after that quick Off/On cycle is back to a 10psi reading and the Kreepy Krauley has picked up its pace indicating the change in pressure was real. I do not see any dirt plumes coming from the returns which might be an indicator of something amiss.

    So basically I'm loosing back pressure that's developed by a partially clogged filter by simply shutting the filter off and turning it back on. In one sense it's great because I don't waste water backwashing, but obviously something isn't right.

    Water is very clear and numbers using TF100 are:

    pH 7.6
    FC 6
    CC 0
    TA 70
    CH 300
    CYA 45

    Thanks


    Edit: This behavior has been a happening anytime I notice the filter is starting to clog. Turning the pump Off, and then On "cleans" the filter.
    Last edited by gtemkin; 07-16-2015 at 07:58 PM. Reason: Additional information
    21K gal 16' x 40' in-ground pool built 1959, old school with Jacuzzi bronze pump, American Products 24" Sand Filter & Americana Multiport valve, Jandy Lite2 millivolt heater, Coverstar cover, and classic Kreepy Krauly.

  2. Back To Top    #2
    Patrick_B's Avatar
    Join Date
    Jun 2011
    Location
    Midland TX
    Posts
    15,001

    Re: Sand filter pressure rises with use then returns to clean pressure with OFF/ON cy

    Mine does the same when I clean the strainer or some such thing. Can't explain it, but mine behaves much the same. I guess things just loosen up a bit.
    TFP Moderator
    Essential Links:
    ABC's Of Pool Chemistry, Test Kits, SLAM Your Pool
    28K Gal IG FreeForm, CLI Quartz, Pentair 36"SF & VS Pump, Dolphin M5, Rheem

  3. Back To Top    #3
    morzh's Avatar
    Join Date
    Jul 2015
    Location
    Jackson, NJ
    Posts
    238

    Re: Sand filter pressure rises with use then returns to clean pressure with OFF/ON cy

    I think when you run constant suction of finely dispersed silt it plugs the top of the sand. When you stop it, there is a backlash from the water in front of the filter and it pushes back a bit, losening and breaking up that compacted top layer.
    Seasonal World rectangular pool, 27K gallons (data sheet), 25.3K calculated
    Jandy Stealth JHPU 2.0 PUMP, 2HP
    Jandy CL340 cartridge filter
    Pentair C320 inline chlorinator
    AquaComfort heatpump heater

  4. Back To Top    #4
    Patrick_B's Avatar
    Join Date
    Jun 2011
    Location
    Midland TX
    Posts
    15,001

    Re: Sand filter pressure rises with use then returns to clean pressure with OFF/ON cy

    Quote Originally Posted by morzh View Post
    I think when you run constant suction of finely dispersed silt it plugs the top of the sand. When you stop it, there is a backlash from the water in front of the filter and it pushes back a bit, losening and breaking up that compacted top layer.
    I like it. Now we need somone to pop in a Gopro to confirm it.
    TFP Moderator
    Essential Links:
    ABC's Of Pool Chemistry, Test Kits, SLAM Your Pool
    28K Gal IG FreeForm, CLI Quartz, Pentair 36"SF & VS Pump, Dolphin M5, Rheem

  5. Back To Top    #5
    gtemkin's Avatar
    Join Date
    Jun 2008
    Location
    Seattle, WA
    Posts
    738

    Re: Sand filter pressure rises with use then returns to clean pressure with OFF/ON cy

    I have had what I think is fine silt on the bottom of my pool. Maybe I'll open the filter and skim a 1/4" of sand off the top. I'll also deep clean at the same time.
    21K gal 16' x 40' in-ground pool built 1959, old school with Jacuzzi bronze pump, American Products 24" Sand Filter & Americana Multiport valve, Jandy Lite2 millivolt heater, Coverstar cover, and classic Kreepy Krauly.

  6. Back To Top    #6

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,077

    Re: Sand filter pressure rises with use then returns to clean pressure with OFF/ON cy

    That's not uncommon for a sand or DE filter. morzh has it just about right.

    When you shut off the pump the flow goes from 60-90 gpm to zero gpm in about 1/4 second. That sudden stoppage of flow dislodges the layer of debris you have been vacuuming into the filter.....almost like returning to clean pressure.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •