Originally Posted by Pod2Vibe
Make sure the flow arrow is pointing towards the black tank and not the hose connection on the outside of your MBS.
Thanks, the black tank flush was one of the first things I tested after reading some stories here about the check valve being installed wrong. The black tank flush seems to work fine and I can certainly hear the spray inside the tank. Happy to now know where the check valve is and can locate it if I ned to troubleshoot and/or monitor over time. Cheers!