Black water flush connection

[DonaandDon]

OK so today while prepping to move, my neighbor asks me to look at his new 5r. New as in a 2020 (Non Jayco). He was attempting to flush his black water tank and wasn't getting anywhere with it. Discharge valve was open, water pressure was great, but no flow. Disconnected and plenty of pressure squeaked out. Reconnected the hose but could not hear or feel water movement. I don't think he "set" the tank prior to and was only there three days (by himself) The conical strainer is in the out position, I want to take the strainer out and push in to unseat the check valve, but will it touch the check valve?

[Robbbyr]

Originally Posted by DonaandDon

OK so today while prepping to move, my neighbor asks me to look at his new 5r. New as in a 2020 (Non Jayco). He was attempting to flush his black water tank and wasn't getting anywhere with it. Discharge valve was open, water pressure was great, but no flow. Disconnected and plenty of pressure squeaked out. Reconnected the hose but could not hear or feel water movement. I don't think he "set" the tank prior to and was only there three days (by himself) The conical strainer is in the out position, I want to take the strainer out and push in to unseat the check valve, but will it touch the check valve?

If it is a dedicated Black Tank Flush connection, and it certainly should be, there usually isn't a check valve at the inlet connection like the regular City Water inlet has. However there is a check valve/vacuum breaker inline and I wonder if it was installed backward.

[EA37TS]

On my prior class C I had an issue wioth the black tank flush and it turned out to be the check valve that is installed in line on the system. My check valve was located in the bathroom under sink cabinet. I replaced the valve and all worked fine after that.

Here is the valve

https://www.amazon.com/JR-Products-5...gateway&sr=8-8

There could also be a back flow preventer which could be malfuntioning or possibly installed backwards.