Pool leak

[Niskybigcat]

My pool has leaked slightly all summer. Now as I am getting set to close it I've tried to figure out where the leak is. I let it go down until it stabilized, right below the two outlets other than the main drain and the outlets near the steps. Then I closed one outlet and left the other open and filled it again. But it didn't leak, so I closed the other outlet and opened the first one. Again it didn't leak. When I open both it leaked until below the outlets, then stopped. So I understand I must have a leaky pipe associated with those outlets, but why would it only leak when both are open? What could cause that?

[Walter]

might be a pressure or water equalization issue.