Originally Posted by 78Buco
Just picked up a brand new Jayco the other day and the dealer was explaining something about the black tank that i have new ran across before. I have always in the past drained the black tank completely, closed the valve and filled the tan back up to roughly half and drained again, repeating this 3 times of so till tank was flowing clear.
Dealer told me this can't be done or the tank with explode from the pressure. Drain valve has to be open anytime the hose is flowing water to tank? Can anyone confirm this? For reference its a new jayco jay feather 30qb
Dealers/manufacturers will specify that the black tank drain valve does need to be open whenever the flush is in use. It is a CYA statement. That is in case the operator becomes distracted and inadvertently leaves the flush going (with the drain shut) and floods the inside of their RV. It will not
"explode" the tank. The tank has a vent pipe from the tank that goes up through the roof to allow odors to exit, AND
to allow the tank to vent when it is draining. Without a vent it would be like a straw with your finger over the end, it won't empty. That vent will prevent overpressurization of the tank.
Having said that the tank won't "explode", it is a good practice to keep the drain open when the flush is going. Have I closed my drain while flushing to build up the water level and then opened the drain? You bet I have. But I am right there and do not do anything else when flushing like that.
Have I also heard of people leaving it run, or inadvertently hooked up to the flush connection thinking it was the regular fresh water inlet? Yes to that too. Water flowing off the top of the roof as well as flooding inside when it leaks thru the toilet. Big time cleanup.