I have an in-ground pool that was installed in the mid/late 80s. It has a vinyl liner and I believe the backing is a black resin/fiberglass type material. There is one skimmer (with two inlets in it) and two return line jets. Previous owner plugged the main drain - not sure why. Pool deck is cement
I am struggling to determine the source of a water leak that is preventing me from starting my pool for the summer.
Here is some history and what I have so far:
Last summer, we had the leak and the local pool specialist believed it was the return lines leaking at the joint right behind the jets. I broke the cement deck behind the jets and we uncovered 1 of the 2 jets was leaking under my cement deck, right at the joint. The repair was done, but the pool was closed for the season. This year, when we opened the pool, we realized we still had the leak as we lose roughly 1 inch of water in 24 hours, only when the filter is running. I ruled out evaporation using the bucket test (and the fact it's 1 inch in 24 hrs!). Another test I did was plugging my jets and two inlets in the skimmer to see if I was losing water from the main drain or liner....absolutely no water was lost. I assumed my return lines wouldn't be the problem (as I assumed the pool repair technician pressure tested them after completed his work) and thought maybe the inlet pulling water from the skimmer was leaking. So I dug my grass behind the skimmer roughly 3-4 feet and ran the pump - skimmer was not leaking, nor the two inlets at the joints connecting them to the skimmer. However, after digging ~4 feet, I did find water! I do see my return lines wrapping around the pool in the area I dug, but the water I found is about 1-2 feet below those lines. Since my skimmer is very close to my main drain, I decided to dig another 4 ft hole in my grass in line with the main drain, but behind the cement deck. Again, I found water....I see the return line hoses (which are not leaking) in that location. Another test I was told to do before a pool technician would come was to remove my backwash line and run the filter in "filter" mode to see if I had water leaking at the filter into the line without knowing - I did this and did not find a leak.
My question is...shouldn't there be some sort of joint connecting the return lines to the main drain somewhere within the area of where the main drain is located (but under the cement deck)? If my deep end is ~8ft, does this mean I need to dig 8ft? I will eventually use a pool technician to locate the leak, however, getting access to one this time of year is going to require a wait of 2 weeks - so I have some time to do more tests on my own. What do you guys suggest I do next? If I am finding water 4ft deep behind my skimmer (which is about 2-3 away from my main drain), what should I look for next?
As for what caused the leak - I believe it happened last year, when the filter was put in a mode other that backwash/filter (my guess is recirculate), with the incorrect skimmer inlet blocked, which caused a pressure on the main drain line that was capped inside the pool.
Any ideas would be greatly appreciated.
Sorry for the long post!