Black tank flush overfill

dougrainer wrote:
OK, one thing that can happen when you do this, it can BREAK the 3 inch down tube from the black tank. The Pressure involved when you do this is tremendous. 45 psi or more has filled the black tank and now the tank has expanded(swollen) and popped either the 3 inch down tube loose or the 1.5 inch vent tube loose. We know this because instead of water coming out the roof vent and overflowing on the roof it came out the bottom from the top of the tank. Because the tank broke open at the tank which is a good thing instead of out the roof vent. NOW, if you do NOT fix the problem on top the tank, you will have black tank odor migrating into the lower bottom cavity because it is NOT sealed now. The RVIA standard for both Gray and Black is to hold water when overfilled. With Black we fill until the water is just below the toilet ball valve and on Gray with water coming into the shower or tub. Also, unless you access and clean out the top of the tank and the underbelly and insulation, you will now have a musty smell all the time. Both inside and out. Doug

IMO that’s not the best way to tell if the black tank is full , for us is an air bubble forms when flushing , and that’s full enough for me . As far as letting it start filling the shower floor that may work for you , but the one time it happened to my wife while showering , she wasn’t that thrilled to be standing in the waste water . We know pretty much our usage on the gray tanks , and every three days or so I just pull the handles for a few seconds , and save enough when I do the black tank to flush the pipes a bit better , then I just empty all three, and start over .