Good evening. In the process of all the work I have been doing on my pool I noticed a considerable leak and have been on the hunt for the source. Its definitely not evaporation as I did a bucket test first and the levels were not the same after a day. Since then I have added a solar blanket so evaporation is essentially nothing now. I got a leak detector and hit the obvious spots with the lights. Nothing obvious there but I have seen some weird things. There is two lights, one on each end of the pool. If I tap on the light I get an air bubble or two that comes to the surface. The dye doesnt get drawn in on either one but presence of air bubbles like that makes me think water is getting out somehow. Using the leak detector I did find a good leak around one of the returns which appeared to be newer than the others. I used some pool putty and patched that up and it no longer draws in the dye. I used the remainder of the dye around the pool at the spots I thought could be leaking but wasn't able to find anything.
Last night I put water back in the pool again and marked the level. Today before the pump came on I checked the spot and I easily lost a 1/4 inch of water. I checked the level again after the pump turned off today and the difference was minimal. To me it seems like the leak is on the suction side in the plumbing which I have suspected all along. So tonight I closed off the returns by placing plastic over them with rubberbands. I then attempted to close off the skimmer drain. I figured if I blocked off all entry and exit points at the pool I could prove the leak is in the plumbing. I have the main drain closed off at the valve, so obviously that is one point where it could be leaking that I cant easily close off at the pool. I am pretty sure based on operation of the pump though that something is already wrong with it, which is why its closed. I am guessing I don't have a good seal on the skimmer drain because its hard to put enough pressure below the water that far. I have a plastic tupperware lid that fits in the groove the skimmer bucket sits on with a coffee cup on top of it. It seemed to be working but when I just looked at it; there appears to be a bunch of condensation like bubbles around the edges. Its at least a foot under water fully submerged so the bubbles forming dont seem right unless they are coming in from the pipe and catching the edges. I have suspected the pipe to be an issue because as I was doing other work I have found a bunch of roots growing through the pipes. I wouldn't be surprised if something got pushed out of kilter of even punctured.
So I need opinions/advice on whether the air bubbles escaping from the light on occasion means water is leaking from there and if the condensation bubbles I am seeing mean the same. Id rather not go on a wild goose chase and focus my efforts on the most obvious. I got to stop the water loss because its going to be costly on my water bill. Thanks in advance!