[BB_TX]

For the black tank flush the procedure is pretty straight forward, but everyone develops their own particular method. I suggest you get a short clear extension to attach to your sewer outlet. Then connect your sewer hose to that. That way you can see what is coming out. Also get a dedicated water hose for the black tank flush.
Here is my procedure as a starting place.
- connect water hose to tank flush connection
- open black tank valve and drain black tank
- turn on water to the flush connection
- close the black tank drain valve for 2-3 minutes
- open the black tank drain valve (you will see more “stuff” come out thru the clear extension)
- close the black tank drain valve for 2-3 minutes
- open the black tank drain valve (you will see more “stuff”
- repeat sequence another 2-3 time until you stop seeing any significant solids
You don’t have to see completely clear water. But good to see few if any solids.
- drain your galley tank and then your grey tank to flush your sewer hose.
DON’t go off and leave the flush water running as you might get distracted and forget.

Word of caution. There is a black tank flush anti siphon vacuum breaker valve in the flush line somewhere in your trailer. Maybe under bathroom vanity. Maybe inside a wall. These are notorious for leaking water inside the trailer. If you do a search for black tank flush you should fine multiple discussions on it and how different members have either replaced it with a better valve, or eliminated it altogether.

Oops! My slow typing repeated what others said above.