I have an in-ground vinyl pool and I use a Polaris 280 automatic vacuum with a booster pump. When I do use the vacuum, a run of about 2 hours, the water level in the pool drops about 2 to 3 inches. This is a significant loss of water, but I do not see water anywhere around the pool or filter. I assuming this is a undergound leak that is caused by the using the booster pump. My question is, how do I go about investigating this leak and what are the possible repair solutions.