Black Tank Flush with Drain Closed? Problems?

[jwcrosby]

We own a 2021 22MLE and love it. I rigged up a short hose to attach to the black tank flush connection from the adjacent spray port. There is a Caution sticker there that says, "Do not use the tank flush valve unless the tank termination valve is in the open position. Can result in an unsanitary condition leading to illness or personal injury." Is the concern here about someone absentmindedly forgetting to shut off the water and consequently overflowing the tank into the trailer? I like to add 3-4 gallons of water after I've dumped/flushed but I'd hate to blow out a seal or something like that if that's a potential problem. Using the black tank flush is a whole lot easier than carrying a 5-gallon bucket of water into the trailer and dumping it down the toilet.

Anyone else doing this? Problems?

Jerry
Sandy, OR