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Thread: Main drain question / help needed

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    Join Date
    Jun 2014
    Location
    Washington
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    9

    Main drain question / help needed

    For the last week, my 8k gallon vinyl lined pool has been leaking water like a sieve. As of this morning, the water is barely left in the shallow end and is down to a couple of feet within the deep end. Given the current water level, the water is below all known openings in the vinyl liner (below stairs, light & returns).

    This weekend, I was able to get the main drain cover off of the bottom and was looking to see if I might be able to plug the bottom drain (where I "think" my issue is). Two openings in the main drain, one on the side I'm assuming is the pump line and one in the bottom, to "drain" the pool. The bottom drain does not have a hydrostatic valve installed. I'm assuming its a float system of some kind, but it "looks" like an open pipe, nothing comes up to the "bottom" of the drain basket, its just open.

    I'm "hoping" this is the source of my issues - 1. my leak and 2. me getting air into my line when I'm running the pump, causing it to deprime the pump when its off (line of thought is if there is air being pulled in right by the main pipe suction line, then it would cause the air to be in the system). But would that seem correct? During the spring, when we had heavy rains in Seattle, my pool didn't loose any water (on the side of a hill). But once I started running my pump and tried to open the pool, I've fought water loss more than I should (note, its nearly emptied the pool in the last eight days since it was filled).

    So for the main drain, should I have a tech come out to investigate the main drain, possibly plug the bottom drain or install a hydrostatic valve in it? Or should I just plug up the whole main drain, including the plum line to the skimmer, and just run the skimmer line?

    As a side note, with all the water loss issues, my liner has developed wrinkles in parts of the liner (installed ~10 years ago by original home owner). In the deep end, where the slope wall meets the floor, it has come away from the seam in the floor and feels "buoyant" against my feet when I was walking along it this weekend. I'm afraid my liner is also shot, but wanted to include for any possible help.

    Thanks for all the help.
    8 x 20 Inground Pool - 3' to 5' deep, WhisperFlo 3/4 HP Pump, Clean & Clear Plus Cartridge Filter, Pentair 300 Off-Line Feeder, MiniMax NT Heater

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    Mod Squad JohnT's Avatar
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    Apr 2007
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    SW Indiana
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    Re: Main drain question / help needed

    A hydrostatic valve is to keep concrete pools from floating. Not needed for a vinyl pool.

    With no loss before you ran the pump, I'd be looking for a leaking return line.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Join Date
    Jun 2014
    Location
    Washington
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    Re: Main drain question / help needed

    Water is below the level of the return lines by feet, I wouldn't anticipate the loss after it dropped below their level. Plus wouldn't explain the loss of prime I have on my pump.
    I could see it in the main pump line from the drain however, it still has water getting to it and would explain the air in the line.
    8 x 20 Inground Pool - 3' to 5' deep, WhisperFlo 3/4 HP Pump, Clean & Clear Plus Cartridge Filter, Pentair 300 Off-Line Feeder, MiniMax NT Heater

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    Mod Squad JohnT's Avatar
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    SW Indiana
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    Re: Main drain question / help needed

    If it leaks when the pump is running, it won't matter whether the returns are below or above the water line. They are pressurized.

    The air and prime loss could be from the low water level. Your pump is working much harder to lift the water with the pool level being low and the suction draining the pump when it is shut off is much greater.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  5. Back To Top    #5

    Join Date
    Jun 2014
    Location
    Washington
    Posts
    9

    Re: Main drain question / help needed

    Prime & air in the line is occurring when the pool is completely full. I haven't ran the pump in a week as the pool has emptied itself.
    8 x 20 Inground Pool - 3' to 5' deep, WhisperFlo 3/4 HP Pump, Clean & Clear Plus Cartridge Filter, Pentair 300 Off-Line Feeder, MiniMax NT Heater

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