Dometic 310 toilet valve, sealed or repairable?

I think they all seem to dribble a little after pumping water in. The real test is to mark the level after it sits for 5 minutes and then check it after 15 minutes. If it rises replace, if it's the same it's normal.

They are a little pricey for what they are, but it never hurts to have a spare. They freeze easily. I bet I've replaced about 1 to three a year for members in our RV club after winter storage. In that case though they crack and leak outside the toilet.