Black tank flush

[jandvis]

The jets in our black tank seem to be stopped up and prevents me from being able to flush the tank after I dump it. Can anyone tell me how to unstop them?

[HappyKayakers]

You probably have a backflow preventer valve somewhere in the line. That may be malfunctioning. Or the spray nozzles may be clogged up. Someone suggested filling the line with vinegar to clear that problem.