Seasons Greetings from UK.

Couple weeks back had a call from regular customer that the top up/balance tank was running flat out. Went to investigate and found the tank was empty and the 1" water main wasn't keeping up with the loss. They were wondering why with the heating on 24/7 the Indoor pool was getting cooler!
Turned the system off and while pondering where to do dye test first the pool level went down a tile. As its an indoor outdoor pool linked with a sluice thought its just balanced out but then noticed another tile appear above the water line.
Ok start around the returns, the water flow into the returns was so much it sucked my hand like a vac point can if you,re not careful and have the pump on Three returns on a common pipe all do the same, as they would!, third tile is now above the water line (less than an hour) so blank all returns off and the loss stops.
Set up temporary feed from plant room to pool so that it can be used for the holidays, that's all working, pool regained heat and only slight loss noted when water supply left off for 7 days.
The water loss is so great we can't hold pressure on the pipe, have tried listening with xlt, water put in and air put in to try and pin point leak, nothing! The prospect of breaking into a floor that has ducting for air handling etc isn't one I've always wanted a crack at.
My plan is to un plug a return at a time and put a cord in and let the water drag it to the leak, do that from the three positions and check cord lengths and then listen, must be something audible like water dropping into an underground cavern one would think. Am a bit loath to put the hydrophone in as there must be a sheared pipe or pushed apart fitting it could get trapped in. Any one with suggestions please add.

I would not hesitate to try the microphone down each pipe, I would also try the Ridgid Micro Explorer to video inspect each pipe,
I would also try listening with your XLT without inducing pressure, just have the pipes open
Please let us know how you make out
Bruce
poolrepairdiver.com

What kind of deck is there? Consider drilling 1/4" holes in easily repaired test locations, to allow inserting a probe to test for wetness and also to insert your XLT listening probe
Bruce
poolrepairdiver.com

Thanks for the suggestions Bruce. Its a quarry tile deck so should be able to drill in the grout ok. Intend to see if we can pinpoint pipe runs with signal and cat scan first. Not sure how successful that will be because of all the air handling ducting (metallic). Am guessing that there is a lot of concrete to get through also to reach any pipe work. Be great to pinpoint to within a foot or so. Will try to remember to take a couple pics as to what we find.

On realy huge return line leaks I've had some luck putting air in at poolside then turning on the pump to put water at the leak. The combination of the air and the large volume of water will sometimes generate some noise when air and the garden hose won't.

Couple weeks time will be on the case so will keep you posted, thanks for suggestions.

We have the leak pin pointed to behind a return fitting. Tried a light string and float from the furthest point first, the string flew in the return, masses of it! tried from the center return and only a foot of string went in. When I was leaning over the edge and put the plug back in, it dawned on me, I could no longer hear running water. Site is a little different, as its deck level and takes a long time for all the drips into the trough to stop. Used the underwater mic so we could hear what was going on, for future reference, ears are still rushing! Will let you know what we dig out.

Thanks for the pics advice,

so you can't attach all at once!

ok so they are not in order!

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