dougrainer wrote:
odds are it is the Black Tank Flush check valve. Doug
That's what and where MINE is!
Looks very similar to this
dougrainer wrote:
OK, NONE of the answers to WHY it is needed are wrong.
1. There is NO way the black tank can backfeed to the fresh system as long as all connections are to factory install and use while camping. There is NO cross connection to the fresh system at all.
2. The REASON the check valve is installed and the REASON it is HIGHER than the Black tank is to keep Black tank odors from migrating back out the Inlet in your water bay. Most OEM installs the inlet does NOT have a check valve like the check valve on the City Water inlet. That is designed so when the black tank flush has completed, when you remove the pressure hose, you will see about a pint of water flow back out. That is fresh water in the line up to that check valve. Then the check valve keeps the odors inside the tank.
3. Aftermarket Black flushes have the check valve either at the tank inlet or the connection has the check valve like on a City Water connection, so there will be NO check valve under the Lavy sink. Doug
1. The reason for the antisiphon valve is to prevent any possibility of black water siphoning back to the park faucet and water supply. Has nothing to do with the RV fresh water system. There is a very remote possibility that under certain unlikely conditions, some black water or black water residue could siphon back to the park or public water system if the antisiphon valve were not present. Same reason a home lawn sprinkler system requires one.
2. The is not true. The antisiphon valve actually provides a direct air path to the the black tank flush head so that any water in the flush line after the valve can driain into the black tank. That is why it is called an Atmospheric Vacuum Breaker valve. All you need to do is look at a cross sectional view of one of those valves. Someone recently posted that their valve leaked and they found that stink bug(s) had crawled in thru the top cap of the valve and prevented it from closing completely.
I removed mine, but installed an external check valve to prevent any possible backflow.
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??????
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??????
