10' x 40' x 4.5' deep vinyl lined pool. Loses, in full summer, 1" per day when the water is above the skimmers. When the water drops below the skimmer the loss is about 1/2" per day. I have read elsewhere that, on average, 1/2" loss per day is due to evaporation. So, it seems that there might be two locations of leaks. In addition, I have seen a water blister on one side of the pool between the steel pool side and the liner. That side is the side where the pool plumbing is located. The blister seems to dissipate when the pump is running. Today, the pump has been off for 2 days and I cannot see the blister.
I have tried locating leaks via dye in critical locations (skimmmers, lights, main drain, etc) and can not find any area where the dye seems to carried away by a leak. This includes the skimmers, one of which has 'surface cracks' in the horizontal lower plane. It seems to be a surface blemish.
Today, I tried pressure testing the skimmer piping and ended up frustrated because I cannot isolate the skimmer loop. The main drain and the skimmers are connected to the pump via a Jandy 3-way valve. Turning the valve to skimmers only seems to almost isolate the loop. When I pressurize the loop and go to the pump I can hear water escape. The noise diminishes as the pressure diminishes. The Jandy valve is hard-plumbed to the piping. There are no union disconnects, so I cannot plug any of the lines. (Is this a "mistake" of installation?) If this were high season and the water was warmer I could try plugging the main drains, not an easy task even when warm and a pool only 4.5' deep.
I am now waiting to see how low the water will go.
All this to ask if anyone has something I am not seeing and can lead me to success?