I'm a pool tech in New York, and I've been seeing a white crystalline precipitate in certain pools. It seems to be a new thing that neither I or anyone else working at my company have seen in the past. It seems to happen in new pools. They are all pools with liners, and salt systems. Commonly it is seen laying on the bottom near the return jets. Initially I suspected it could be a result of too much salt, but salt levels are usually around 3000ppm, and even after vacuuming it out on waste, it shows up week after week. It looks almost like granular conditioner/stabilizer laying on the bottom. One of our techs said that he collected a sample and that it was very hard.
I'm wondering if it could have something to do with the water we use to fill new pools. The water comes from an underground lake situated in limestone. We've been using this water supply for years, and never had the problem until about 2 years ago. Has anyone seen anything like this before. Any ideas?
Water chemistry is typically well balanced, as we regularly maintain the chemistry.