Black tank flush no worky

Thanks to all of the answers ,it was the check valve under the sink and for $ 4.00 everything is working perfect! Thanks to all of you again!

You mention it is the first trip of the season - was it winterized for the cold season? We forgot to winterize ours one year and it stopped working. The check valve (under the bathroom sink) failed and leaked water all over the bathroom floor.

oldcat1 wrote:
On a fairly new RV I would guess the Anti-siphon Vacuum Breaker. Ours failed at two years old. It's a $10 part. Usually located under the bathroom sink.

Safe travels

Ours is located in the wall (had to cut through the kitchen cabinet) behind the shower stall...great planning there.

The check valve on our tt was installed backwards.

I've looked and there is no vacuum breaker,check valve inline on the water line. I have located the valve under the sink ,is there a way to test it to see if its good or bad? Thank you for all the help

On a fairly new RV I would guess the Anti-siphon Vacuum Breaker. Ours failed at two years old. It's a $10 part. Usually located under the bathroom sink.

Safe travels

Ours works...sometimes. "Better" results when we have higher water pressure.

OEM installed flush system

3 items

1) Inlet....usually has a screened washer and a internal check valve (like city water inlet).....screen clogged and/or check valve defective

2) Anti-siphon Vacuum Breaker.typically inside bathroom sink cabinet or a closet
Some have check valve in outlet to tank that can jam
More common issue is leaking water all over the inside of RV when they fail

3) Spray nozzle head.........holes get clogged with minerals.
Hard to clean usually just abandon in place and install new