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Thread: Fine grit not caught by sand filter

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    Fine grit not caught by sand filter

    Any ideas on how on permanent solution for a fine grit that is not caught by sand filter? We constantly have a fine layer of dirt that settles on bottom of the pool and gathers in spots especially where liner not perfectly flat. If you come near it with a vacuum or step near it just clouds up and disappears into the water. I don't think my sand filter is taking it out well and it just resettles. We vacuum it up but 2 days later it is back. I think part of it is coming from the large flour mill that we live next door to. My chemistry is perfect. Water is clear and we can easily see this stuff settled on the bottom. If I add DE to my sand filter my pressure goes way up fast so assume it is collecting it but I can't keep adding DE constantly as I would be backwashing every time I turn the filter on.

    Our city water is awful and rusty too so that doesn't help. We have a house water filter and our fill water is now going through that too but the filter will go from white to rust in a matter of several days.

    We did replace the sand in the filter this year hoping it helps and not hurt? (Yes I know the sand never needs replaced but was going to deep clean the sand before start up and assembly was on so tight when we tried to get the part up the whole latteral assembly came up out of the sand. Couldn't get it back down in sand so vacuumed the sand out and instead of trying to figure out how to get the wet sand back in just went with new dry sand that was really easy to pour from the bag) I will say the sand had pool store chemicals ran through it as previous owners did not use TTP. I found TTP when I couldn't get water to clear after buying the house and after 2 pool stores nothing worked. Yes I used the expensive stuff they sold me with no help before I found TTP. TTP users were great and pool cleared up in no time and will not step back foot in the pool store unless I can't find something at Menards or Rural King.

    Any ideas on how to get a very fine dirt out of the pool? The previous owner said they always had the stuff settle to bottom and easily vacuums up. So it has been happening for years which is why I think a lot of it is mill dust. I just don't have time to vacuum ever other day.
    18x33x4 oval Above ground pool- 15300 gallons, sand filter, full sun no shade
    tft-100 test kit
    Central Illinois

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    Mod Squad woodyp's Avatar
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    Re: Fine grit not caught by sand filter

    If it's constant, it may just be something you have to live with. I do. Instructions in Pool School on how to add some DE to your sand filter to help it catch some finer stuff. Vacuum a lot slower at those trouble spots. Good luck.
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
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    Mod Squad JohnT's Avatar
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    Re: Fine grit not caught by sand filter

    I suspect one of two things. First, it may be dust that settles into the pool and never gets pulled into the skimmer so it never has a chance to be filtered. To check for that, I'd suggest running your pump 24 hours a day for a few days and see if it improves. If that makes no difference, then I'd elevate your chlorine to shock level for a few days while continuing the full time pump schedule and see if that helps. I've had a few instances where my chemistry was good but I had algae trying to grow and leaving fine dust on the floor. A few days of elevated chlorine cleared it up.

    Seems like living in farm country can cause both of those issues.
    TFP Moderator
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    Re: Fine grit not caught by sand filter

    Also, try a skimmer sock. I don't know if it would catch all the super fine stuff, but in my pool it catches the pollen.
    12500 AGP 2HP Sand filter
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    Texas Splash's Avatar
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    Re: Fine grit not caught by sand filter

    Hummm. It's one thing for something nearby (i.e. mill dust, or pollen) to settle/sink in the water, but it's another to think it might be related to the filter's ability to sift it out. Because of your location, and suspect water source with what may appear to be metals in it, how about posting a full set of test results for us? Just so we compare levels to make sure we're not missing something chemically-related that may be contributing to your problem.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Re: Fine grit not caught by sand filter

    Yes live in farm country without a doubt. We had this problem last year when we bought the house and old owner said he assumed mill dust and constant since he put the pool in years ago. Last summer we did a SLAM and passed OLCT several days in a row before quitting and ran pump 24x7 always and still had this issue. Old owner always ran pump 24x7 when pool was open. Was hoping to start off better this year in hopes someone had out of box idea but think we are just going to have to live with it. If we sweep the pool (with filter running) it is back an hour later. If we vacuum it is back within a day or 2.
    18x33x4 oval Above ground pool- 15300 gallons, sand filter, full sun no shade
    tft-100 test kit
    Central Illinois

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    Re: Fine grit not caught by sand filter

    8 times out of 10 the problem is dead algae settling to the floor.

    You are saying "grit" but is it gritty? Can you catch some of it between your thumb and finger?
    If not, you need chlorine in your pool. No need to think out of the box, these issues are always pretty simple once the problem is identified
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Fine grit not caught by sand filter

    I have been doing overnight chlorine tests several days in a row with no loss. This morning I actually gained chlorine? Was 6 last night based on drop test and 7 this morning. Combined Chlorine has been consistent at 0.5

    CYA - 45
    PH 7.5
    CH - 250
    TA - 120

    We can't touch the silt or whatever it is. The pool is way too cold to get in.. only 55 degrees. And last year it always dissipated as soon as you got close which makes it very hard to vacuum since I think it just clouds up into the water before the vacuum comes over it. I figure we just going to have to live with it but thought I would try. Between the mill dust and the trucks going to it very dusty on occasion. We also can see a fine layer of dust/dirt on top of our solar blanket so assume this would be what is ending up in the water,.
    18x33x4 oval Above ground pool- 15300 gallons, sand filter, full sun no shade
    tft-100 test kit
    Central Illinois

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    Re: Fine grit not caught by sand filter

    Have you tried the skimmer sock like heikejohn mentioned? I just started using one again for the season. WOW! Was there a bunch of stuff it picked up. Fine, powdery, yellow in my case. Pollen for sure. Glad it didn't get on the filter cartridges.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Fine grit not caught by sand filter

    Sounds like you have exhausted the proper SLAM procedures and are indeed a victim of living near a very dust area after all. I suspect effected water surface circulation is exceptionally important for you at this point. I'm out in the country with just one skimmer, so I get my fair-share of dust and grass that blow onto my water. But I do have 6 jets that help keep water moving towards the skimmer .... unless the wind is pushing away from the skimmer. I'm not sure of your AGP set-up, but if you have any way to add additional return jets or angle them to improve circulation perhaps that might help. One of our favorite tricks is to drop a few ping pong balls or Styrofoam popcorn peanuts on the water to see how well they move towards the skimmer. That might help you confirm how well your water circulates.

    Also, did anyone ever suggest for you to consider deep cleaning your filter? The sand can become compacted and channeled over the years reducing its efficiency. You might want to look into doing it when you get time. Deep Cleaning a Sand Filter
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    Re: Fine grit not caught by sand filter

    Thanks for the suggestions. skimmer socks are ordered. We ended up with brand new sand this year due to pulling the laterals out when trying to deep clean the sand before starting the pump up so figure it is ok. We only have 100lb sand filter so figure stuff is going through it and we only have one return and the one skimmer. Will try the ping pong balls and check circulation. Maybe I will try a slime bag or something on our return and see if that helps.
    18x33x4 oval Above ground pool- 15300 gallons, sand filter, full sun no shade
    tft-100 test kit
    Central Illinois

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    Re: Fine grit not caught by sand filter

    had swept the dirt into water early last evening when adding chlorine as vacuum hose broke and was hoping stirring up the piles would send some to filter. Right before bed had found socks had been delivered so ran out and stuck one on. Checked it this morning and gross... yes I know I have maple seeds ... crazy things... skimmed as many as I could last night before putting solar cover back on. The "dirt" on the skimmer sock is almost cottony... not grainy, not slimy. There is also tons of little blue pieces in it that absolutely no idea where it came from. skimmer.jpeg
    18x33x4 oval Above ground pool- 15300 gallons, sand filter, full sun no shade
    tft-100 test kit
    Central Illinois

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    Texas Splash's Avatar
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    Re: Fine grit not caught by sand filter

    My pool also MUST have skimmer socks in it at all times. They work wonders. Very good!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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