northeast

Am hoping that someone on the forum might be able to provide some much needed advice on an expensive repair we are about to undertake. We have owned our house for approx. 10 years. We have a 16x32 inground, vinyl-lined sand bottom pool. Just a few years ago we had to replace our vinyl liner and the next season when we opened the pool our water level was low and we had little sand mounds poking up little hills under our line only in the deep end around the edge where the sand and the walls meet. As we had just had the liner put in the year before and we had recently upgraded our pump, filter and repaired an entire return line, we weren't about the plunk down more money for something that appeared to be cosmetic at that point. Jump ahead a few seasons and we opened our pool this year, and our water level was extremely low. We attempted to fill the pool only to notice that we started loosing water immediately. Our pool repair person took a look and thought our liner was shot, probably due to a tear from the sand mounds. We were told that the only real solution to keeping this from happening to another new liner would be to address any water issues, i.e. ground water, water table, etc. We never had any issues before that particular year as far as ground water and we never had any after the initial sand mounds appeared in the deep end. So here we are contemplating replacing the liner again and installing a vermiculite bottom. We've been told that we may need drainage work but no one seems to know for sure. We've also been told by some contractors that putting a hydrostatic valve in would keep us from having issues again. Others have suggested it wouldn't help. Any advice, thoughts, etc would be greatly appreciated.