Black tank backflow preventer leaks

[Mooresoc]

I’m a brand new Keystone owner and noticed a small leak in the bay storage. I narrowed it down to the bathroom sink where a backflow preventer keeps black tank from flushing into water source. I saw a lot of people saying these plastic ones break easily so I replaced it with a brass version. Still leaks. So, I made sure the fittings were tight with plumbing tape. Still leaks. So, I’m considering removing it all together and replacing it with a standard elbow since my source is a separate and specific black tank flush hose and shut off from possible contamination. My fear is that when I don’t have the hose hooked up, won’t it just leak all the way into the control area where the black tank flush valve is? Other thoughts?

[notanlines]

Odds are at this point that you may have replaced the valve with the water flow in the wrong direction. It is very common for the factory to install these valves incorrectly. At least give this a try. Check and see if it is in the proper direction.

[Mooresoc]

Thanks for the response! I did check the flow as I saw similar posts about that. I followed the line from the black tank flush inlet and made sure that the arrow of the backflow preventer was entering the black tank and not the other way around.

[sourdough]

Is the brass valve itself leaking or the connections going into it? If it's the connections something isn't right in the way they are connected - they don't (shouldn't) lead once properly attached.

If you wanted to you can remove the anti siphon valve completely, install a couple of elbows on the two pipes with a small tubing bridge between them and eliminate the valve completely. If you do that use a vacuum break on the end of your flush hose like the one in the link.

https://www.tractorsupply.com/tsc/pr...yABEgLXNfD_BwE

[Jester]

Mine started leaking in my previous RV because I was using the black tank flush with the black tank gate valve closed. This builds pressure in the black tank and forces it out of those connections. Never run your flush with the gate valve...dump valve ...closed.