We had our pool remodeled this past summer. Before work began we knew we had a leak and prior to work beginning the contractor did all kinds of leak tests and discovered a leak by one of the returns. He said he fixed it and work began. Since then the water level remained constant with no problems. Last week though we started having some below freezing weather here in north central Florida. No rain much this winter. I started noticing the water line getting a little lower by the skimmer. Sunday night it got to 32 degrees around 11:00 pm and did not get above freezing till around 8 in the am. I made sure the pump stayed running, covered exposed pipes, and did not see any signs of water around the pump pad. Last night in the 30’s and 40’s. My question is last night I filled water to a certain tile level and this morning it had gone down about an inch. Is it possible that if this contractor “fixed” this leak with some sort of putty or compound that the colder weather / pool water could somehow cause it to fail and allow the leak to resume?
I don't see anything on the pad that would contribute to water loss that you wouldn't otherwise see. Still seems odd that a repair below ground would fail in cold weather since the soil should provide adequate protection. But I'm sure stranger things have happened. Don't rule-out the possibility of a new leak developing though. The pool light (niche) or around the skimmer are possibilities. If you have a main drain, I suspect you have a hydrostatic valve, so it might have become defective or gotten jammed with some junk around the seal. We'll watch for updates though.
Don't let the water level drop too far below the skimmer though. Maybe a foot or so, but not too far to where you risk the shell shifting. If it continues to drop that far, it may be related to a return, the pool light, or the drain's hydrostatic valve.