location of main drain pipe

[sks24]

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

[PoolDoc]

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.

[sks24]

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.

[PoolDoc]

The hydrostatic valve, if there is one, is in the bottom of your main drain:
http://www.a1poolparts.com/-strse-83...lve/Detail.bok

[sks24]

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.

[PoolDoc]

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.