Valve is leaking while pump running on filter

[Poconos]

Welcome to the forum.
Quite possibly the spider gasket has a bad section around the waste port. Or, it popped out of its channel in the valve housing and got deformed. These gaskets are glued into the channels but eventually can loosen. Seems to be a common problem. I'd open the valve and take a peek. Mark the valve position, put the handle in an intermediate position to relieve the spring force on the valve, then remove the 6 screws. Once you look inside you'll see the gasket and the problem may be obvious. For the time being I'd just run the waste line back to the pool if you can so you don't lose water. Some people on the forum don't believe they can be fixed successfully but I say bah...sure they can. I've done it. One thing you should never do is switch positions with the pump running. Thought I'd be a wise guy and learned the hard way.
Hope this helps.
Al

[bayshorebevo]

Thanks a bunch, Al. Will take a look at it when I get home. Posted that before I went out of town to work for a couple days. Thanks again.