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Thread: location of main drain pipe

  1. #1
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    Default location of main drain pipe

    Thank you for allowing me to join your forum. I need help determining the location of the main drain pipe which goes from my main drain at the bottom of the pool to the pump/filter. The reason for my asking is that I am all but certain that I have a leak in that pipe, and I would like to try and repair it on my own. (If I cap the main drain, the pool doesn't leak.)

    I have both photographs and drawings/diagrams of my pool, and would of course be pleased to post them upon being enabled to do so.

    Here's a link to a (shared Google doc) diagram of my pool:
    https://docs.google.com/drawings/d/1...it?usp=sharing

    It seems like the main drain pipe would run out from under the pool to either the east or the west. If it needs to run under the skimmer, then it would run to the west. I hope that's not the case, because there's a concrete pool deck which would run over the pipe if it runs around the pool tub on the west side of the pool. If it runs out to the east, the access to the pipe will be much easier, as the deck would not cover much of the the drain pipe, and I could easily dig under it safely.

    Thanks in advance,
    Scott
    Last edited by sks24; 08-02-2014 at 01:34 PM.

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    Default Re: location of main drain pipe

    It would make sense that builders would follow a consistent pattern in the way the locate pipes . . . but in my experience that's not true. I've seen pipes run just about every way they could have been.

    About the only thing you can rule out, is any path that would have required the builder to cut through rock.

    You *might* get some indication of how it runs, if you dig down and follow the line for 6 feet or so away from the equipment pad.

    One caution: the MD pipe COULD run under the entire pool, to reach the drain. OR it could run around the walls (from either side) and then drop under the pool. For several reasons, there's a fair chance that the section under the walls is the location of the leak . . . and fixing a leak their is a major task. Usually, it's easier to run a new line.

    One suggestion: verify that your pool's hydrostatic pressure relief fitting and valve ( IF it has one ) is not the source of the leak.

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    Default Re: location of main drain pipe

    Thank you for your reply PoolDoc. I don't think I have any kind of pressure relief fitting. Here's my equipment pad, and here's the top of my sand filter. When I try to turn off the skimmer with the pump running, and open the valve so that water can come from the main drain, the pump loses its prime because it sucks in air, presumably from the hole that's in the MD pipe (which, again, must be at the same level as my returns less @ 4 inches). I can bring a little water in from the MD, but only if about 75% of the intake is from the skimmer.

    My main drain intake at the bottom of the pool does run off to the east, which is the side of the pool that the equipment pad is on. Here's a pic of the east side of the pool.

    What comes to mind is to start digging just south of those black chairs that you see (that's the east side of the pool (I'm looking from the north)). If I'm lucky, the pipe runs under the concrete deck where the deck is relatively narrow, and the leak would be easily and safely accessible and repairable.

    Running a new MD line would involve digging under the pool all the way to the bottom drain hole underneath the pool, no? This would no doubt require a permit, and cost thousands? I've seen solutions which involve running a new liner inside the pipes. Are there companies which sell kits to do this, or is there a DIY pipe liner solution? I saw one company, but apparently they're out of business.

    The soil around this pool is very sandy, and so the digging would be easy to do by hand.

    Again, thanks for your help with this matter.

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    Default Re: location of main drain pipe

    I think there may be one in the MD next to the intake. I think I recall seeing two elements: the drain intake, and something else, which could be the hydro valve. Tomorrow I will dive down there and take a look at it. I think that there could be an "O" ring failure such that it would allow water through until the water was shallow, after which there wouldn't be enough pressure to breach the O ring. So that could account for the very specific level to which the water descends. But the inability to draw water exclusively from the MD? It seems like that air would have to come from a hole in the MD pipe.

    Thanks.

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    Default Re: location of main drain pipe

    When hydrostatic valves fail, often it's because they've opened, and allowed ground water to flow into the pool -- what they are supposed to do -- but also allowed a bit of grit or organic matter to enter, and wedge the valve open a bit.

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    Default Re: location of main drain pipe

    I didn't look at that drain today to verify whether there's a hydrostatic valve there. But I'm pretty sure there is, not least because when I drained the pool completely last month water would seep back into the pool via the MD, and very quickly. The water table is quite high here. I did try to remove the MD grate when the pool was empty, but there was no obvious way to do so.

    Bottom line at this point is that it appears that the first order of business is to control for this valve. Since I don't have scuba gear, it looks like I need to drain the pool again, remove the BD grate, and just go ahead and replace the valve using the valve tool they sell at that site you linked to above. I guess I'll buy a new grate, too, since I might have to destroy the one which is on there now to get it off.

    But my inability to get the pump to keep its prime if I try to pull more than about 25% of the water from the bottom drain concerns me. It seems like the only circumstance which could account for this would be a hole in that MD pipe.

    A somewhat related question. I noticed a new problem yesterday on my equipment pad. When I run the pump with the selector which is on top of the sand filter set to either "Filter" or "Recirculate" some water leaks out of my exhaust drain. It seems like the handle is pretty hard to turn on that selector. What might be causing this? This just started yesterday. Here's a pic of the flow with the selector set to "Filter" : https://drive.google.com/file/d/0B4q...it?usp=sharing

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    Default Re: location of main drain pipe

    Quote Originally Posted by sks24 View Post
    Bottom line at this point is that it appears that the first order of business is to control for this valve. Since I don't have scuba gear, it looks like I need to drain the pool again, remove the BD grate, and just go ahead and replace the valve using the valve tool they sell at that site you linked to above.
    Do NOT drain the pool when the water is high; even concrete pools WILL float out of the ground. If you must drain, you MUST lower the water level around the pool.

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    Default Re: location of main drain pipe

    Thank you for your reply PoolDoc,
    Whoever had this house before us - we purchased it in 1997 - drained the pool when the water table was high, and the pool did lift out of the ground about an inch on the west side of the deep end. I've drained it perhaps three times over the past 15 years when it was dry, and it's been stable. About 18 inches of water will seep into the pool when the water table is low. Anyway, I will be careful to wait until we haven't had rain for awhile. There's a creek about 100yds south of the pool which all but runs dry occasionally, and that's when I empty the pool.

    So is waiting until the rain subsides, draining the pool, and replacing the valve a reasonable way to proceed at this point? I realize that you would want to be very careful about specifically recommending any particular course of action. Please don't concern yourself over the consequences of anything I might or might do at your suggestion. I'm not going to fault you in any way if things go wrong. I'm sure I've agreed somewhere not to sue anybody over anything that might happen here, and of course that would be my preference, as I want for people to feel free to offer their best advice.

    Thanks so much for your help,
    Scott

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    Default Re: location of main drain pipe

    Actually, I don't have enough money to make me a target for any attorney with an IG above the double digits!

    My caution is more ignorance based: the sort of situation you're in tends to include surprises, even for very experienced service guys.

    I would recommend checking the hydrostatic valve, simply because it's (a) a likely cause, and (b) one that can be repaired. Some of the other possibilities involve MAJOR expenses and demolition. In those cases, pool owners often end up abandoning their main drains.

    On a positive note, the mere fact that you've repeatedly had water enter the pool via the hydrostatic valve greatly increases the chance that that valve IS the problem.

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