Thanks for both replies. After I posted I decided to do a bit of research on the Thetford site. The leak may yet be coming from the fitting and not the valve. No water leaks when I flush. After a few hours of non-use the water accumulates (I placed a container below the fitting). So, I may have messed up the fitting installation. I don't have time to mess with this right now and I have a large enough container to handle a few days of accumulation. When I do get to it I will replace the fitting again and this time I will be extra cautious doing so. If that doesn't work I will replace the valve. The Thetford site had a good tutorial on how to replace that. Thanks again for the advice. I will post when I have fixed this issue.