Originally Posted by timfromma
Bacteria and other nasties from your black tank can and do exist in your rinse pipe. Your shower is connected to your fresh water system and connecting that to your black tank rinse can allow this bacteria back into your fresh water system. It's the same reason why you don't use your drinking water hose to rinse your black tank.
Not gonna happen. There are one way valves on the shower output (mines not a shower...just a connection for the OEM supplied 15 foot coil hose) and the black tank flush line. Also, since the flush connection is a few feet above the black tank how is anything going to travel UP to get into the hose?
You'll be more likely to get contaminated water from the fresh water tank, even if you didn't have a black tank installed. Having seen the inside of fresh water tanks during routine maintenance has taught me to never drink that stuff.