What if I open the by-pass valve only half way? not completely open, the pressure will be less and if it over fills it will gently make its way to vent over-spilling on the ground (if that happens) I would also have my timer buzzing every 5 minutes.
I've added a winterizing inlet, even if I have a heated garage and all the plumbing is in the heated area of the camper (above floor).
It's not like I'm adding it, I haven't started to build it yet so, it will cost 3$ more, if you guys say I might need it one day, that's good enough for me, I won't argue for 3$.
I also added two hose connections on the lowest points at the end of the plumbing lines (hot and cold), I needed to add valves anyway to drain the lines, I might as well add hose valves.

