A better explanation is needed. You cannot bypass the black tank or leave the valve open because the solid waste will not keep flowing across the bottom of the tank and all the way out the hose to the sewer connection. The solids get left behind and build up in the bottom of the tank. The slope on these things needs to be perfect and it takes a lot of water to keep things flowing. So, you must collect the waste and dump once in a while, flushing with a toilet or bucket full of water to get the solids to move. This does not happen in the grey tank and they can be left running. However, those of us who live in RV's collect grey water before we dump the black tank, so we can use it to flush the hose after dumping the black tank..
Full time boondocker, solar powered, no generator