On my unit the black water flush lines are blue PEX lines. One line goes up inside to a back flow anti siphon valve. The other line returns from the valve to the black water tank flush nozzle. These valves are often a disaster in that they leak and flood the inside walls. They are required by code but I generally rip everything out and trash it. Anti syphon and backflow prevention should be done outside the RV. I attach mine to my hose at the pylon.
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William & Sara
2012 Silverado 2500 HD DA
2014 Cedar Creek 38CK
Linear Mode
