Why are there two slide valves on the black water system- one right at the tank and the other in the normal spot where grey and black join for dumping? Which one should be opened first?
I've got a 28z and I think its done in case something in the road hits/breaks the drain pie going across the bottom of the MH. I hookup the drain hose and release the one on the driver side then walk around to the passenger side and do it.
I had this discussion with a 28Z owner that did not have the passenger side valve on his unit. I had tank heaters and he did not we did not know if that was the reason; to make sure the pipe did not freeze. I open the driver side first and then the passenger side for the thought it would give the material he chance to get a running start. I am sure it practice it doesn’t matter much