Finding a leak

[bluenoise]

I have determined my in-ground plaster pool has a leak "somewhere," but I don't know where to start looking for it. Here is what I've found:

1. If I don't run the pumps (booster is currently disabled while I try to figure this out), the water level goes down about 1/8" or so per day, which matches my bucket test results. So, the pool leak is insignificant when the pumps don't run.

2. If I run the main pump for nine hours, the water level goes down about 5/8". I have all the jets turned downward to keep from perturbing the surface, in case the turbulence increased the rate of evaporation. So, it seems my leak is costing me about a 1/2" of water each day.

I cannot see any leaks in any of the visible plumbing or solar array and none of the ground is visibly wet. Most of the pipes leading to and from the pool are only about 10-15" below the surface and only those immediately around the pool (drain, returns, etc.) are any deeper than that. The equipment pad is below the pool's water line, so I'm baffled as to why it doesn't leak even with the equipment off, unless the return pressure is adequate to overcome the leak's otherwise trivial flow. I assume the leak is in the return side as it's the only part that's pressurized when the equipment runs, right?

The surface area of my pool is about 420 square feet, so the rate of loss translates to roughly 15 gallons per hour, by my rough calculations.

Has anyone used a leak detection service? What do they cost? How does it work? Is there a DIY leak detection method I should try? Is this a big enough leak to detect or even worry about?

Thanks in advance

 

[vincent]

Bluenoise, the simplest test you can DIY is disconnect your drain pipe from your multiport valve (even a little slack from the joint should be good enough), run your pump in filter mode. Check if any leakeage from the drain. If yes, your multiport valve is leaking. I am not familair with your piping system, so I can't say much about other leaks.

Good luck.

 

[bluenoise]

Thank you, Vincent. Unfortunately, I don't have such a valve on my pool. There is one pipe coming to the main pump from the skimmer. The drain leads to the skimmer, which has a simple flap that I close to split the draw between the skimmer and the drain. I will try opening that flap so virtually all of the water to the pump comes from the skimmer to see if that affects the situation. I suspect, though, my leak is on the pressurized return side of everything, since it's only measurable when the pump is running.


Edit: I just reread your post and I think I misunderstood what you were saying. I thought you meant drain, like at the bottom of the deep end, not drain as in the type to remove water from the pool. If you're describing the latter, I don't really have that, either. I have a 1-1/2" threaded connector onto which I can attach drain hose and that's controlled by a ball valve from the main pump, but there is no hose attached and it's not dripping.

 

[vincent]

Bluenoise,

If you don't have any piping going anyway else apart from your pool and back to your pool only, then the leak would have been on the return line. Like I say earlier, I wouldn't be able to help you much without knowing what you have but if you have to do a pressure test, look out for your SWG. It may not be meant for very high pressure.