Need Help Identifying Part

[Wisconsin Retiree]

This black type valve is located under my bathroom sink. It has 2 white PEX lines one running water to it and the other returning in the same direction it came from. So essentially a u turn they this part. What exactly is it for? Anyone familiar?

[Mikendebbie]

A big advantage to reading this forum is learning about stuff that i have no personal experience with or troubles on my RV.

I think that is a vacuum beaker for the Black tank flush system. See pic below. Lots of threads on the subject. The OEM valves are prone to leak at some point in their lives. Some folks have removed them, connect the pipes together and use a hose end backflow preventer at the faucet. Some folks have replaced the valve with a high quality brass valve. Do a search.

[Wisconsin Retiree]

Ok, that makes sense. I had flushed my tank earlier today and when I was just packing up I found water dripped in the pass through storage. I traced it to this valve and now everything makes sense. I appreciate your help.

[RMcNeal]

Unfortunately most of us have had these plastic valves break. I just removed ours, cut the pex loop out and put an elbow in behind the basement wall. I got an external backflow preventer/vacuum breaker to put on the hose connection in the convenience center.
https://www.amazon.com/Merrill-BVBNL...428703&sr=8-13

[DQDick]

This is the same thing we've done on all of our Montanas.

[Daryles]

Replace it with a brass one.

[Wisconsin Retiree]

Ok, will do! Thank you all for the information greatly appreciated.

[twindman]

Mine rig had a similar looking backflow valve. I was able to unscrew the top and there was a little ball in the chamber that would stop the back flow. I just removed the ball and have had no problems since. You can always add a backflow valve outside.