I have a 20x40 vinyl lined pool. Last Summer the pool started leaking about 1 inch/day, but only when it is hot outside.
Only leaks when hot outside
Only leaks when system is running
It is not just evaporation. I have done the bucket test on and off for the past 8 years. (the pool was constructed 20 years ago by previous owners and we put a liner in it 8 years ago) The pool historically has lost 1/4 inch per day during the Summer. I can live with that. I figure that its evaporation.
One of the returns has had a leak for 8 years presumably. It has always blown air bubbles for 2-3 minutes at pump startup.
I ran the pool through the Fall, Winter, and Spring with increasing time on the timer. No major water loss for the past 9 months.
The last two days have been over 85 degrees and the pool is down 2 inches from Saturday when I last noted the depth.
Last Summer when this started, I drained down below the skimmers and removed the skimmer bezels. There was a leak between the skimmer and concrete on the West side of pool and I used silicon to fill the gap. I didn't find a leak on the East side skimmer.
I am guessing that the water is leaking around one of skimmers when the concrete expands to a certain point.
I know that the system is old, I get air equalizing sounds when the pump shuts off, I have a drip at the filter....
Basically, can anyone tell me what to look for?
I am going to have to recheck my skimmer repair with some fresh gaskets and some Pool Putty.