zorr59 wrote:
I was once told by an RV salesman that he would fill 3-5 gallons of water and then add a couple of small or 1 big bag of ice. The ice would slush around and help break up harden solids. Never tried it just found it interesting
The ice last about 5-10 minutes before it melts most of the time, even less in the hot summer.
Usually the ice is melted before the RV gets running down the road.
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The most important thing for black tanks is to use plenty of water while flushing, and never leave the tank completely empty. The only reason to leave a tank completely empty would be for winterizing after completely flushing the tank.