leaks ,don't leak

[REBARBEE]

last two years after closing the pool , after cold weather came on started losing water all the way down into the deep end. went ahead filled back up and had to add water every day as long as it was cold or cool, now that hot weather is here losing every little if any, some to evaporation. can not see any thing obvious. anybody have any ideas

 

[atttech-2]

Wild speculation but if you have one the loss could have be the hydrostatic valve, either it got some debris in it that eventually flushed out and it subsequently closed or the spring is getting weak and contracts causing it to open when cold now that it is warm it expanded and and closed.