Fresh water leak

[Gunsmoke]

I have two white hoses behind my shower that are joined at a black valve. As soon as we turn on the fresh water fill the water comes pouring out of the top of the black valve. Can anyone help me determine what the black valve part is so I can order a different one? Thank you.

[dagst1]

Hello.

If you could let us know what you are working on -- year make and model it would help us help you.

A picture would help but to venture a guess it sounds like the vent/check valve for the black tank flush. But without more information it is just a guess.

[Gunsmoke]

I’m working on B a 2021 Crossroads Cruiser 30RLS.
Not sure how to post a picture.

[dagst1]

Thank you for the picture. That is the check valve/ vacuum breaker for the black tank flush. Not uncommon for them to leak. Just need to replace it. Some are plastic and some are brass. Just search for RV back flush vacuum breaker and you will find it.

[Gunsmoke]

Thank you!

[Russb]

I replaced the vacuum breaker with a backflow check valve with hose threads and installed it on the hose connection for the black tank backflush. I had three failures with the vacuum breaker resulting in a flooded bathroom. You should be able to connect the two white hoses together if you decide to remove the vacuum breaker.

[Papa-T]

Copied from Recpro.com: The purpose of this valve is to prevent water supply contamination from backflow and back-siphonage. When you are using the freshwater to flush the black water tank, the contaminants are flowing out through the tank. Once you stop the flow of water, however, there could be pressure that wants to push the contaminated water back up through the flushing system and into the freshwater source. The vacuum breaker check valve stops this, leaving your freshwater source clean and uncontaminated. **********************************************Me: this is why you should always use a separate hose designated just for flushing out the tank. Or at least I do.

[Russb]

This is what I used to replace the vacuum break backflow preventor. I also use a separate hose as Papa-T suggested.
https://www.lowes.com/pd/ProLine-Bra...ter/5013024155