Black Flush Line?

[MASTERDRAGO-5TH]

I'm thinking about removing the vacuum breaker under our sink. I sometimes smell stink from the black tank and want to eliminate possible leaks. The Thetford toilet has not been an issue (yet) - valve sealing and no drip from flush lever. So a couple of questions. Is the connection (pictured) have a check valve inside it? It looks like it does. Also what fittings do y'all use to connect the two tubes? I can either do it where the vacuum breaker is removed or under the floor where the tubes originate.

 

[jcurtis934]

If your tubes for rinse connect to the device under the sink I would remove it and connect those two together with anything that makes it a straight line. Since I have pex, fittings, and the crimp tool, I made my own. Fitting in center does have a valve. I connected a short hose to it so that I wouldn't wear out the plastic threads.

 

[1retired06]

If you don’t have a PEC crimper, sharkbites are easy.

 

[DQDick]

Did mine in the old rig and the new with shark bites. We use an external backflow preventor on the outside. They're available at most hardware stores and Amazon.

 

[waynemoore]

2X DQDick said

 

[mtlakejim]

Yes there is a cheap plastic check in that connection. If you have pass thru in front of that compartment it is easy to access back of panel and remove wing fitting off back followed by taping the check out with a screwdriver. Doing so significantly increases flush volume!!

You can eliminate the backflow valve too. Especially if you add hose with ball valve to the outside hose fitting (IE: the same fitting mentioned above). In fact doing so and using clear hose allows me to use my 12volt on board water pump to rinse black tank via the outside shower connection!! Very handy when a good rinse line is not available at dump station!

If access under the bathroom isn’t too hard you might consider cutting the line below the floor as it would keep any future leaks below your floor level. Not a major thing as that line isn’t used much but just a thought.....

 

[MASTERDRAGO-5TH]

Okay. Thanks. So Shark Bites under floor to connect the two tubes. Then connect something like the Watts 288a out at the black water flush inlet. Or no backflow but use a ball valve at the outlet of the hose being used for flushing?? Does anyone know what size the pex is? What size Shark Bite. I'll bet underneath there is enough room to use a coupling direct.

 

[BuilderBob-MOC]

I did are's under the the floor cut all the exter pipe out and used crimp fittings!