I just replaced the existing Waterway multi-port valve on a Millennium 27" sand filter with the same Waterway MPV. The valve immediately began leaking under the gasket where the threaded sleeve meets the manifold. Thinking it was a 'lemon', I returned it immediately and replaced it with the same Waterway MPV. It worked for about a week, and then began leaking again at the same spot. I have tried everything from the marine lube to the rubber mallet tightening technique. I've backwashed the filter many times with the same results. When I spoke to Waterway, they said the threads on the sand filter manifold may have been damaged. I looked and cannot see any visible damage. Does anyone have a similar situation and a solution? Thank you.