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Thread: pentair fns 48 diatomaceous filter has started gurgling

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    Join Date
    Jul 2016
    Hilton head island south carolina

    pentair fns 48 diatomaceous filter has started gurgling

    the gurgling seems to be coming from the top of the filter where the pressure release valve is...i have read other posts suggesting air in the filter so i've opened the release valve while its running and let the water run out and i've also opened it while the pump is not running and i left it open until no more air escaped...still gurgles...this has just started in the last week or so and we have owned the house since may so it ran fine for several months...i am new to pool maintenance, and the pool company that i used instructed me on how to clean the pool but they neglected to tell me i needed to add diatomaceous earth every time i backwash so i have never added it possible that this is the issue because i have back washed all the filter material out of the filter...i have some on order and until then i am running the multiport on recirculate instead of filter...thanks in advance for any advice
    i have an in ground freeform pool that i think is approx 10k gallons...the diatomaceous filter is a pentair fns 48 but i have no idea how old it is because we bought the house used...i think the pool was installed in 2002 so it's probably 14 or so years old

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    Mod Squad Texas Splash's Avatar
    Join Date
    Jun 2014
    South-Central Texas, Marion/San Antonio

    Re: pentair fns 48 diatomaceous filter has started gurgling

    Hello and welcome to TFP! Sorry for the delay responding. You are correct in that generally when you backwash or do any other type of cleaning to your filter, you'd want to replenish the grids with some DE to ensure they remain covered. Leaving grids exposed can cause damage to the grids themselves. Gurgling would first seem to indicate some air/water moving around in the filter housing. You might ask yourself how could air be entering the system? So perhaps first ensure you have no suction side air leaks that may allow air into the filter. Pool School - Suction Side Air Leaks From there, you might find yourself at a point where you need to open that filter and look at things for yourself to inspect the grids, upper/lower manifold, and any other parts to ensure there is nothing wrong carrying-over from the previous owners. Here are a couple DE links that may help you get going:
    DE Filter Cleaning Tutorial
    Use and care for DE filters

    There are others here at TFP if you do some searches from the search box above. Hope this helps. Let us know, and welcome to TFP.
    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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