Old-Biscuit wrote:
Bet one of the inner seals has come dislodged and it now 'rolled'
Regardless....if flushing doesn't fix it, gonna have to get to valve and rebuild/replace.
Easiest access is to cut three side window under valve area and fold down underbelly section (folded area towards front and tape shut with gorilla tape)
X2, just get the rebuild kit and replace the seals since you have to take it apart anyway. Note that there are 2 major brands, Valterra and another brand I don't recall the name of at the moment. Easy job once you get the tank dumped.