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Cuda67bnl · 05-05-2022, 06:40 PM

Used the black tank wash/flush line today for the first time while dumping on our way out of a campground. Noticed it was leaking behind the wet bay area, and stopped immediately. Got home and pulled the access panel off to investigate. I expected the water line for the flush to go straight to the black tank from the hook up. But it goes up into the floor of the coach, presumably behind the shower, then comes back down to the black tank. What gives? Does it just go up, then loop straight back down? I changed the fitting going into the tank and fixed the leak. But wondering why it’s ran that way. It doesn’t tie into anything else, right?

amosnandy · 05-05-2022, 06:49 PM

Quote:

Originally Posted by Cuda67bnl

Used the black tank wash/flush line today for the first time while dumping on our way out of a campground. Noticed it was leaking behind the wet bay area, and stopped immediately. Got home and pulled the access panel off to investigate. I expected the water line for the flush to go straight to the black tank from the hook up. But it goes up into the floor of the coach, presumably behind the shower, then comes back down to the black tank. What gives? Does it just go up, then loop straight back down? I changed the fitting going into the tank and fixed the leak. But wondering why it’s ran that way. It doesn’t tie into anything else, right?

There is a vacuum breaker and backflush valve up in the coach somewhere. That is what is leaking.

They are there to prevent black water from the tank from being able to get into city water or the freshwater tank. Mine failed last year. It is about a $3 part that depending on access is a 2-3 hour job to replace.

Skip426 · 05-05-2022, 06:51 PM

At the top of the plumbing , there is a vacuum break ; mounted above the water level of an overflowing toilet , to stop nasty " stuff " from backing all the way down to the connector in the wet bay should the black tank be over filled .

RV applications these are plastic and fail often , brass replacements are available.

I'd heard before that some manufacturers hid them ; but usual install is behind the vanity sink .

Cuda67bnl · 05-05-2022, 07:06 PM

Quote:

Originally Posted by amosnandy

There is a vacuum breaker and backflush valve up in the coach somewhere. That is what is leaking..

The leak was from the fitting going into the black tank. But thanks.

Old-Biscuit · 05-05-2022, 08:15 PM

FYI

Cuda67bnl · 05-05-2022, 09:08 PM

Thanks.. this is where my leak was. I swapped the fitting and all was well.

oceanos · 05-09-2022, 11:48 AM

Quote:

Originally Posted by Cuda67bnl

I changed the fitting going into the tank and fixed the leak.

Does your's look like this? Curious how you changed the fitting? My fitting that is on the tank itself is cracked and was leaking. I fixed it with glue and a clamp, but would rather replace it at some point.

https://photos.app.goo.gl/mrxMKzqjyU29MyL38

Cuda67bnl · 05-09-2022, 12:54 PM

I changed this…… It screws into the fitting that’s in the tank. The threads were messed up and didn’t seal the fitting to the rubber washer.

andy29847 · 05-09-2022, 04:31 PM

Quote:

Originally Posted by Old-Biscuit

FYI

See the note by the vacuum breaker on the black tank wash line. It's not supposed to be installed where venting can do damage. apparently, very few people who build RVs know this. On my alpine coach the vacuum breaker was between the pantry cabinet and the shower wall. Access was through a panel in the rear of the pantry cabinet. When my vacuum breaker went bad, it didn't leak - it flooded. Lucky for me I had access to a shop vacuum and was in the desert where it was hot an dry. It still took a full day to make things normal.

BTW, I have seen several of these on other campers installed under the bathroom sink.