I purchased a home this summer with an in ground pool. I noticed the water level going down during the hot days but figured it was evaporation. Now with the cooler weather (Pacific Northwest) we are no longer using the pool but plan to keep it open for the winter months. I noticed the water level was going down by about 1/2 inch per day so started a leak detection process using the bucket method and blocking the skimmer and return lines to eliminate the piping. I also used the dye method to check all underwater fittings and steps. I have concluded that the leak must be in the vinyl liner. The water level kept going down but has now stabilized about 5inches below the normal level and well below the skimmer. I assumed the leak must be at that level but can not seem to find anything around the water level that would indicate a leak (dye test and tactile). My question is would the water level only drain down to the water table level out side the pool (quite high as I am close to sea level and the rainy Northwest) and could the leak actually be below that level? There is no main drain at the bottom of the pool.