As their NAME implies they are an 'ANTI-SIPHON' 'Vacuum Breaker' 'BACKFLOW PREVENTER'
Anti-siphon so Contaminated black waste liquid does not flow out the flush connection
Vacuum breaker because they allow atmospheric air into flush system and stops any negative pressure which could allow siphoning from waste tank
Backflow preventer because internal Disc closes and physically stops any back flow
They can fail.......disc hangs up and doesn't seal off opening to atmospheric air thereby allowing flush water supply to spray inside the RV (typically under bathroom sink, in closets and some are even behind the shower wall......none are ideal spot due to water leaking)
LOTS of things would have to fail in order for black tank waste liquids to backflow.
Supply water source would have to quit
Black tank liquid level would have to be extremely high....high enough to be above top of piping for flush system ie: backed up into vent line high....in order for waste liquid to backflow.
That means waste tank line to toilet would have to be pressurized/toilet bowl seal holding/not overflowing in order for waste liquids to back up high enough in vent line to force liquids thru the flush spray nozzle into flush lines up to connections where anti-siphon valve was and then out side of RV into water supply system.
Possible...........sure
Probable ...........Not very likely
Besides a simple hose end vacuum breaker would be all that is necessary should anyone CHOOSE to eliminate the piece of junk anti-siphon vacuum breaker backflow preventer valve inside their RV so that WHEN it leaks it doesn't cause damage inside their RV
Hose bibb vacuum breaker
Anti-siphon vacuum breaker backflow preventer valve (RV Flush System)
SO YES.they can be removed -----hard piped if OWNERS choose to do so.
Then just attach a hose bibb vacuum breaker to flush connection and SAME prevent is in place WITHOUT leaks inside the RV
NOW if OP would just reply whether or not this is the valve he is asking about??????
