Is this Laz? If so, first, thanks for the invite to JB a few weeks ago. I couldn't reply to your email due to how gweb email works.

You can usually isolate the skimmer piping from the pool by inserting a threaded plug into the return port at the bottom of the skimmer. Depends on your model, but you might need a 1-1/2" to a 2" threaded plug. If you winterize your pool you probably already have these on hand.

Most pools have a standard hose bib "faucet" installed somewhere in the pool plumbing, usually over by the pool equipment. You can get a couple of brass fittings that allow you to thread an air port onto the hose bib so you can attach an air compressor to that hose bib. Sort of like this:

I'll plug all the pool outlets with plugs to isolate the plumbing from the pool. Then pressurize each isolated plumbing run to about 20-30psi. With the various valves plumbed into your pool, you can usually isolate different plumbing sections and pressure test them to see which one loses pressure; cleaner return, pool return runs, spa, skimmer, etc.

If all of your plumbing holds pressure, it could be structural. A leak around a port or the skimmer box set in the pool's shell, etc. Those can sometimes be identified by the water dropping down to a certain level and then dropping no further. Or by using a dye test.

Some leaks are easy to find. Others tough. A specialist near me uses a listening device to pinpoint the sound of water/air bubbles gurgling through buried tubing.

Thanks, Mongo. Yep, this is "Me." I appreciate the insight on the pool thing. Sure, C'mon over to JB Forums. Your experience and expertise would be quite welcomed!

Thanks again, my friend.......

Have you done the bucket test with and without pump running to verify actual water loss vs. evaporation and to verify if it is in the lines or the shell (around light, around jets, around skimmer, or crack)?

A suction side leak (prior to pump) does not usually cause water loss because it sucks air and does not leak water. If you have a leak while pump is running it is after the pump to the return lines.

I was unable to do the pressure test mentioned above because I could not get a positive seal on the skimmer hole no matter what I tried. I only learned this after I built a homemade air/water pressure tester for about $35. I also could not hear any leak with the homemade pvc/stethoscope I built.

Everyone kept telling me underground leaks are not very common so be sure and check everything above ground really well first. We had a a freak freeze in the desert where at least the top 6" or more of my pool froze and I am sure that is when it happened. We don't shut down pools here and I didn't have any electricity to circulate water.

I dug around the pool located the moist spot about 14" down, cut a 24" hole in the 5" concrete decking and started to dig. The leak was just under the skimmer.