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Thread: losing vacuum pressure and main drain valve replacement

  1. Back To Top    #1

    Exclamation losing vacuum pressure and main drain valve replacement

    This is a commercial pool, but it is small as far as commercial pools ago. Only 38k gallons.

    We have 3 skimmers, one of them we attach the vacuum hose to and the manual pole vacuum. The other 2 skimmers, we put in plugs (2" pvc with caps) which we fill with water, turn upside down and hook into the skimmer holes.

    After hooking all those up, we go to the pump area, then we close the main drain valve until we reach the desired vacuum pressure of 15 inches.

    I don't know why, but sometimes I get good vacuum pressure and most of the time, I don't get much. When I first started working here, we used to get the pressure to 15 inches then we start vacuuming. Now I'm lucky to get 10 without the pump losing water... then we gotta open the main drain valve a bit until the water catches up and maintains.

    I am thinking it's the main drain valve, which hasn't been replaced in about 10 years. The motor has been replaced a few times over the years, the sand filter is about 5 years old, I'm getting good circulation (around 130 GPM).

    Also, what's the best tool to replace this main drain valve? It has 2 unions, but they're so large that our largest pipe wrench won't fit around it. I'm thinking it'd be too tight for a strap wrench.

    -38,000 gallon pool and 1600 gallon spa
    -Triton II TR140 sand filter
    -In ground

  2. Back To Top    #2
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,879

    Re: losing vacuum pressure and main drain valve replacement

    The main drain valve is a very likely possibility. A strap wrench is certainly worth a try on the unions. If that doesn't work you are going to need to get a larger pipe wrench.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  3. Back To Top    #3

    Re: losing vacuum pressure and main drain valve replacement

    Yeah, I don't get why the pump would lose water like that
    -38,000 gallon pool and 1600 gallon spa
    -Triton II TR140 sand filter
    -In ground

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