Side note:
The valves are located up front and there is a long run of pipe from the valve to the drain cap.
It takes TIME for the long pipe run to completely drain AFTER the valve is closed.
Extremely important:
When dumping, make sure that the camper is tilted in the direction of the drain cap.
Front to back and side to cap.
Other wise, undrained liquid will remain in the pipe.
And, the next time it's time to dump, the drain cap will have a lot of liquid built up behind it.
That is NOT due to a leaky valve. . .and can lead to an un-necessary repair.
Previous owner could have made that mistake. Dealer wouldn't know that was the case and would have simply changed out the valve and did a $hitty job of it.