Thanks James. So what is the best way to test this? Do we just get a new gasket, and if that works, problem solved? Our system is starting it's 4th season I believe. We were getting ready to change out sand once we get the pool cleaned out, etc. Do you have any idea what the life expectancy on the type filter/pump we have, by chance? Guess I'm wondering if this multiport valve would most likely be the culprit for a system the age of ours. I have no idea how long these things should hold up!