Our in ground pool has a leak whenever our pump is running using the skimmer line. Our latest test showed 1/2 an inch in 10 hours. We tried isolating the leak by shutting off the pump and plugging all return lines and we did not lose any water. When we run the pump using the bottom drain line we do not lose any water, either. We thought we had a leak in our skimmer line, but all my lines were pressure tested and they all held 20 psi. I have been getting a small amount of air bubbles in the pump when we run our vacuum on the skimmer line, but it seems to disappear if I blend the skimmer line with the bottom drain line (maybe like 80/20 or so). Anyone had a similar experience? Any suggestions on what I should do next? This is my first post, sorry if I left any information out. Thanks in advance!