First are you able to empty the tank?
The valves are bolt in place, if you are able to empty it the part are available almost anywhere (RV supply store) Valtera has the part for replacement.
The second option there is a twist on valve that can be applied and get you home.
TWIST ON VALVE
Have you ever delayed fixing an old valve problem? Now just twist a new valve onto your current waste valve bayonet fitting and eliminate messy replacements or expensive service!
T58PART NO.DESCRIPTIONPRICET58Twist on valve24.03