About 7 weeks ago we bought a home with a 20 year old in ground concrete pool. We're total pool newbies and are trying to learn as much as we can about how to care for the pool.
About a month ago, we had a salt cell installed and really like it. Last week we started losing water, both when the filter was running and when it was off. The rate of water loss seemed to be about the same whether the filter was on or off. When the water dropped down to the bottom of the skimmer opening into the pool (with the filter off), the water loss stopped. We haven't loss any water in the 1 1/2 days since the water dropped to this level. There is still water in the skimmer basket area and that hasn't gone down below the level of the rest of the pool. We noticed a lot of damp soil at the edge of the concrete apron at the lowest point in the yard, but it has dried out a bit since the pool stopped losing water.
The pool is older and has a few cracks that a past owner filled, as well as a few newer looking ones. A pool guy comes out weekly to help us monitor the chemicals in the pool and he used pool dye at cracks and didn't notice anything being drawn into them.
There is a pipe coming from the filter area (I think this is the backwash pipe) that empties in a drain by the driveway and it isn't leaking. Out pool guy also checked the o-ring in the multiport and it was fine.
Any suggestions for other things we could do before calling a leak detector? And anything that might put our minds at ease that this isn't a huge, expensive problem? Thanks!
Approx. 15,000 concrete pool built in early 1990s, sand filter, Hayward salt cell.