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Thread: PJD's 2012 Leak Detection Thread: Loosing 1" every 24h hours

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    PJD's 2012 Leak Detection Thread: Loosing 1" every 24h hours

    Hey Folks,

    So I've got a serious leak in my pool. The pool was built around 1980 using what i think is a somewhat unusual design. I haven't seen another like it anyway. It's gunite on the bottom with a steel/concrete reinforced fiberglass wall.

    In any event, I've plugged the skimmers and three return eyelets. I haven't closed the valves at the pad, do I need to do that to?

    Do I need to swim down and block off the main drain somehow as well?

    My plan is to measure the loss compared to the bucket over the next 12-20 hours and document that information. I'm concerned its in a return line and I'm also concerned I had multiple failure points. Anecdotally I don't notice loss when the pump isn't running but I need to capture data methodically and go from there.

    Any other steps I should be taking?

    Here's a picture of the pool. It's worth noting that several years ago it wasn't winterized properly and the deep end skimmer line was damaged rendering that skimmer inoperable (this is why we can't have nice things). It's permanently sealed off at this point. I'd like to return that to functional but I need to find the leak first.

    38,000 gallon In-Ground, gunite bottom/fiberglass wall (older style I've not seen elsewhere)
    Sand Filter, Hayward 1HP SuperFlow 2 (not sure flow rate)
    Built @1980

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    JasonLion's Avatar
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    Re: PJD's 2012 Leak Detection Thread

    There is no fixed set of things to try. This is strictly a try things till it stops leaking process.

    If you block all of the inlets and outlets then you can rule out the plumbing as a possible source of leaks. That means blocking the main drain(s) as well as the skimmer(s) and return(s).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    PJD's 2012 Leak Detection Thread

    Some suggestions... (it's an imperfect art)

    1. Mark the level with a pencil on the skimmer with time and date. Run the pump 24 hours, mark and note the loss.

    2. Mark the level again... Keep the pump off for 24 hours, mark and note the loss.

    If the loss is approximately the same on both days you should be thinking in-pool leak. Fiberglass panels with vinyl or other bottom types often have seams that develop leaks from roots and insects, etc.

    Turn the pump off to stop water movement, then try to snorkel slowly with a mask and test the seams with a syringe with food coloring (a needle puts a thread of color by the suspected area). Move very slowly. I find most leaks in this type of pool where two panels meet the bottom material and form a tee. Patch with a two part epoxy pool putty. A little bit goes a long way.

    If you loose substantially more water with the pump running, suspect the return lines. This can be confirmed with a pressure test.

    Good hunting!



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    Mod Squad Bama Rambler's Avatar
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    Re: PJD's 2012 Leak Detection Thread

    Quote Originally Posted by PJD
    Anecdotally I don't notice loss when the pump isn't running but I need to capture data methodically and go from there.
    This makes me think of a leak to waste when running. Have you checked the backwash line to make sure it isn't leaking when the pump is running?

    If it only leaks when the pump is running but it's not backwash valve leak, then it almost has to be a return line leak. And it's most likely above the waterline. That's where I'd concentrate my efforts first.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: PJD's 2012 Leak Detection Thread

    Thanks for the reply guys. I plugged the returns and skimmers and left it for 24 hours and had no real loss.

    I opened up the returns and skimmers and turned on the skimmers BUT NOT the main drain and ran for 24 hours and lost an inch.

    I have just opened the valve to the main drain and I'm hoping to see if I loose the same amount over the next 24 hours or if I loose more.

    If I loose the same amount then its either the one functioning skimmer or 3 return eyelets.

    Anybody have a good step by step guide for pressure testing a line?
    38,000 gallon In-Ground, gunite bottom/fiberglass wall (older style I've not seen elsewhere)
    Sand Filter, Hayward 1HP SuperFlow 2 (not sure flow rate)
    Built @1980

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    Re: PJD's 2012 Leak Detection Thread: loosing 1" every 24hou

    Ok, here's where I'm at
    24 hours with everything plugged (except the main drain) no loss
    Skimmer and returns running only - 1 inch in 24 hours
    Skimmer, returns and main drain - 1 inch in 24 hours

    Is my next step to pressure test?
    If not what is my next step?

    Quote Originally Posted by Bama Rambler
    Quote Originally Posted by PJD
    Anecdotally I don't notice loss when the pump isn't running but I need to capture data methodically and go from there.
    This makes me think of a leak to waste when running. Have you checked the backwash line to make sure it isn't leaking when the pump is running?

    If it only leaks when the pump is running but it's not backwash valve leak, then it almost has to be a return line leak. And it's most likely above the waterline. That's where I'd concentrate my efforts first.
    I've been thinking more about this. THe backwash line isn't underground, I can see it and there is no loss there. That's where you're talking about, right? The line off the pump when I hit backwash or rinse?
    38,000 gallon In-Ground, gunite bottom/fiberglass wall (older style I've not seen elsewhere)
    Sand Filter, Hayward 1HP SuperFlow 2 (not sure flow rate)
    Built @1980

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    Mod Squad Bama Rambler's Avatar
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    Re: PJD's 2012 Leak Detection Thread: Loosing 1" every 24h h

    When you ran on main drain only was the skimmer plugged?
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: PJD's 2012 Leak Detection Thread: Loosing 1" every 24h h

    Quote Originally Posted by Bama Rambler
    When you ran on main drain only was the skimmer plugged?
    I didn't run the main drain with the skimmer plugged, here was my rational:
    Pump off, returns/skimmers plugged, main drain not plugged - no loss
    Skimmer and returns on, main drain valve shut off but not blocked at the bottom of the pool 1" loss
    same as above but with main drain valve on 1" loss.
    I figured the loss only happens when the pump is on and it's the same if the main drain valve is blocked or flowing so it must be the skimmer or one of three returns.
    Is that logical?

    Maybe the rumrunners my girlfriend has been making in bulk are hindering my efforts.....
    38,000 gallon In-Ground, gunite bottom/fiberglass wall (older style I've not seen elsewhere)
    Sand Filter, Hayward 1HP SuperFlow 2 (not sure flow rate)
    Built @1980

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    Mod Squad Bama Rambler's Avatar
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    Re: PJD's 2012 Leak Detection Thread: Loosing 1" every 24h h

    It's most likely the return line.

    I would plug the skimmer and run on main drain only.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: PJD's 2012 Leak Detection Thread: Loosing 1" every 24h h

    Ok, thanks, I'll give that a go. I may wait till after the fourth, I'd like to keep it clear for the holiday then dive back into it.

    I used the search function but I don't see much for how to find a leak in the return line.

    Any thoughts? Can you pressure test a return line and is that the next step? I'm about ready t call a leak detection company but I don't know any in my area. One I saw had a whole page on their site dedicated to the evils of SWGs......
    38,000 gallon In-Ground, gunite bottom/fiberglass wall (older style I've not seen elsewhere)
    Sand Filter, Hayward 1HP SuperFlow 2 (not sure flow rate)
    Built @1980

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