Black Tank Flush

[Goldwing0848]

When I Backflush Black water Tank I get water from somewhere running into the coach
I have the settings set for Sanitizing.

[Spower]

Black tank flush is usually a black colored attachment that the hose screws into. If my trailer is set to sanitize it will fill the fresh water tank.

[Goldwing0848]

Just purchased this new Jayco Melbourne.
Put hose on bottom fitting On the Melbourne top fitting is for city water and bottom for tank flush.
Opened up the tank to flush. Turned on the water and water started coming into coach from wall behind toilet. It was clean water.

[RBW]

On my unit I put the water hose on the black tank flush inlet, open the black tank drain valve, and turn on the water tap. I usually cycle the black tank valve to let the water partially fill the black tank and then reopen the black tank valve to let it drain. I believe this helps to reach the sides of the black tank. By the way, I use a different hose from the one I fill the fresh water tank with. My second hose is dedicated to black tank operations only. Some have felt that wasn't necessary in past posts but it makes me feel safer.

[Marcm157]

Originally Posted by Goldwing0848

Just purchased this new Jayco Melbourne.
Put hose on bottom fitting On the Melbourne top fitting is for city water and bottom for tank flush.
Opened up the tank to flush. Turned on the water and water started coming into coach from wall behind toilet. It was clean water.

That is a sign of a defective check valve. They are usually installed behind walls which makes them inaccessible to replace.

[Goldwing0848]

Originally Posted by Marcm157

That is a sign of a defective check valve. They are usually installed behind walls which makes them inaccessible to replace.

Thank you ! I read that we had a check valve but had no idea where it might be located.
Trip back to the dealer!!! Thanks

[Dskyward]

I found mine behind the shower stall wall from linen storage 2 years ago while reversing the shower C/H valve-handle in our NorthPoint fifth wheel. Cold water was leaking into the hot line, making hot showers not that hot, so I simply flipped the valve. Two extra pex water lines coming up out of the basement underbelly...I didn’t know what it was for, until recently accessing the furnace reset switch. Jayco wants the black tank rinse inlet line to travel way vertical, enter the check valve or vacuum breaker and take a U turn 7’ back down into the black tank. The $20 part is plug n play.

[FishNFarm]

They are probably the same folks complaining about their water tasting funny.