I have had my pool for about 2 years now and think I may have a leak. I don't leave the autofill on all the time, but if I leave it off for 2 - 3 weeks I notice the water getting close to the bottom of the skimmer opening, sooner if we aren't getting much rain. I also have to constantly add salt, probably 8 - 12 40 lb bags since last spring. When I look in the autofill, there are 2 openings in the bottom under the water line. One is connected to a pipe that goes to the pool. The other hole is open to the ground. Did my builder forget to plug this hole? It seems like it would be the source of my water loss, but before I plug it I wanted to make sure there isn't a reason for the hole to be open. Also, any recommendations for plugging it if needed?