What you have is a Valterra product the coach builder use and installed. It appears the kit comes with a back flow preventer but without inspecting the installation there is really no way to know for sure. I suspect you have one otherwise once the tank level reaches the height of the flush nozzle it will start to drain thru the system. You can call Tiffin to verify but I would craw under the coach and look for it just to be sure.
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I put a bronze "90" on my black tank inlet, with a simple shutoff valve attached. I leave them attached all the time, and turn the valve off after flushing. I obviously only hook the green hose up when flushing the tank. As stated earlier, the shutoff allows me to control the flow of H2) at the tank and not the faucet while flushing the tank. The "90" lets everything clear the bay door.
I have a flush sustem on my RV. I am sure there is a BF device. I always sget a little water dripping out when I remove the cap to install my hose but it is clear water (no brown lumps) The hose connection is above the tank so I also have gravity on mt side. The advantage of a BF is if you were to disconnect the hose from the supply before removing from the flush commection you would siphon poo water.
2inAlabama.......Connect a hose to the flush connection and do your flush. Turn the water off, but leave the hose connected at both ends. Wait a few minutes, maybe five, and then disconnect the hose from the FLUSH connection. If you get a bunch of water flowing back out under some pressure for a few seconds, you have a backflow unit installed. If there were no backflow valve in place, there would be no water running out, it would have drained into the tank.
Don & Mary
2005 Monaco Diplomat 36SKT
2012 Chevrolet Silverado LTZ CrewCab 4WD
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