Ken;
Forrest's suggestion has resolved that problem for many. But in case it doesn't, here is a copy of the post I made in August of 2006 and haven't had the problem since.
I may have the solution. I have messed with the seal, rotated the seal, greased the seal and replaced the seal. It would last for a few weeks (of constant use) and then start loosing water again. This last time I replaced the ball valve and the seal. The ball valve is slightly larger and now goes well past the edge of the seal. So far, it seems to be working. My suspicion is that the ball valve was redesigned after we took delivery of our units.
And just as an added item, the plastic front cover on the base is held on with Velcro. I looked for screws and didn't see any so just yanked, and voila, there it was.
John