Originally Posted by VinceU
There's a vac-brk in the flush water line about three or four feet above the black tank nozzle entrance. Wherever your leak is showing, go inside and try to locate the valve about chest high. Could be closet or behind access panel. They often fail, available at Home Depot.
"Laws are made to be broken", however this is one I would considered it....
"The Public Health Service Act is a United States federal law enacted in 1944. The full act is captured under Title 42 of the United States Code (The Public Health and ... " Look up the Fed rules re potable water and connections here.
RVIA didn't require probably close to a million RV and boats to be fitted with this Vac breaker for nothing! All new homes have them also whenever outside connections are made to drinking water, even RV parks have them fitted.