I've had a leak for a few months. It's an inground vinyl pool, about 6.5 years old. The pool was losing an inch every couple days in the summer, and even in December it was losing about 1/4 inch per day (air temps in the 30s to 50s). I did do the bucket test and the bucket had zero loss for several days. There is also a wet area in my front yard where the grass is soggy/muddy even though we've had almost no rain, so I think that's where the water is going.
I had been adding water to keep the pool full over the past few months, but recently decided to let it drop and see if the leak would slow or stop. It has slowed -- the water level is now below the skimmer and the water loss is about 1/10 inch per day. I have visually inspected the liner and I tried food coloring around the surface and near the skimmer and returns. I did not find any leaks. There do not appear to be any leaks at the equipment pad.
I called my pool builder and he said he would need to drain the entire pool and get behind the liner to find and repair any holes, for $500. He said it was very unlikely that there would be leaks in the plumbing or skimmer box.
Does this seem reasonable?