Originally Posted by silver suz
I thought It ran all the time if the pipe was connected to the drain.
well, it does...if you leave the dump valves open.
Which some people do. but it isn't recommended to leave the black tank open while hooked up to sewer; the toilets use such a low-flow of water, there isn't enough to push things along down the pipe. So you should let the tank fill...then let it all go all at once with a big wooosh!! for good measure, most people then fill up the black tank w/ just plain water, and let that go "wooosh" for a good rinse.
Its fine to leave the gray tank valve (if you have one
) open when hooked up to sewer, though. Most people like to let the gray tank fill up on the last day of their stay, so that they can dump that after they've emptied the black tank....gives the slinky a good rinsing w/ soapy water.