I have an elevated spa. When the pump is off the spa drains significantly overnight. The check valve is fine. Actually there is a manual diverter valve before the check valve that can either be set to pool or spa that is always set to pool so I don't think water can get back through there. I use the spillover to divert water to the spa but when the pump is off so is the spillover. Where else can the water be going and how? I've done a bucket test without any significant difference in level.
I appreciate any responses. Thank you
I appreciate any responses. Thank you