A few months ago, we were losing water to the waste pipe when then pump was switched on. We changed the spider gasket and that fixed the problem. Our pool has an overflow pipe and after the heavy rain we've experienced in Houston, the overflow pipe was not flowing. I flicked the pump valve (Pentair model SM-20-2) from "filter" to "waste", in hopes of clearing the pipes. When I flicked it back to "filter", water continued to pour out of the waste pipe. I turned the pump off, but water continues to pour out, just more slowly than when the pump was on. This has been going on for more than two hours so it's not looking like it's going to stop, and I can't understand why it's occurring when the pump is off (when we had the spider gasket problem, there was no water loss when the pump was off). Please help!