[patodonn]

Well, you know that pesky placard next to the flush connector that days "Don't do it" unless the tank valve is open? Here is what could happen, and almost did to us.

Flushing the black tank, and, as always, with the black tank valve closed to refill via the fush system to get a good "second" flush. I always use 7 minutes from empty, which is always safely below "full" in our rig. Got distracted with something and it went 10+ min. Now, THAT is overfull!

Where did it go? Not really absolutely certain, but the toilet assembly and seal held and it didn't leak into the bathroom, (thank God). It appeared to start to fill up the black tank vent pipe. When I shut off the water in a panic and then opened the black tank valve, the pressure of the effluent was enough to crack my 3 yr old and somewhat brittle sewer hose in two places and leak significantly for about 1 min. It looked like I had several feet of water column pressure behind it at the start. Bit of a mess to clean up afterward, and needed a new hose, but, other than that, got away without damage to me, the surroundings, or the Monty (except the sewer hose)

I was REAL lucky! Tank is not leaking and nothing overflowed, but I can visualize black tank water pouring down from the roof of the Monty, or the tank rupturing from the pressure of a 10 foot column of liquid in the vent pipe.

Think I'll be a bit more attentive to the task at hand next time. Word to the wise....be REAL careful and attentive if you are going to use this flushing technique.

Best