We hadn’t taken the bedroom headliner down yet, so today while trying to decide where to wire cable for a potential additional tv in the back, we pulled it down. It’s amazing how much dirt collects on a ceiling in 43 years! We decided to take a looksie between the shower and wall to check out the hot water tank and various pipes. So glad all is dry and then it was time to figure out what the heck that pipe is for. Posted the question on the GMC site on Facebook and within minutes there were answers. It seems to be a vent tube whose end usually has a screen to keep out bugs. That tube needs to be mounted so the open end raises above the top of the tank. The “open end” doesn’t attach to anything. Your sure-flow valve looks like it is meant to let in air (ie, when using water, air must flow in to replace the water that is being pumped out) but not let water out. I am happy with that response, it makes sense to us. We will replace the hose though unless we can get the kink out. We keep on keeping on.