What is this valve?

[DJ18]

OH man! nothing like a nice warm day prepared to get wet and/or dirty to figure things out. My poor trailer, it's a wonder the water system worked at all! Things I learned today:

1. the city water inlet has a white cap to cover the inlet and what I assume is a pressure regulator. that cap was not tight, and it needed to be. It was the source of all the streams and puddles of water.
2. our water heater has an aluminum tank and no leaks. once all the water and mud and wet cardboard were removed, we could see and feel it was dry. We do need to replace the pink insulation with something on one side.
3. on mine, anyway, to fill from the fresh water inlet, the fill bypass valve has to be open. when it is, there is no air pressure preventing easy fill of the tank.
4. when the tank is full, the valve has to be closed for the pump to pressure the lines.
5. Just guessing and asking about your theories is no substitute for taking the time to remove everything that keeps you from seeing the area where problems are and thinking it through.
6. some things are just a two person job.

[KYAvion]

Sounds like you don’t have a check valve at your city water inlet, which allowed water to exit when your water pump was running. I removed the check valve as well and installed a ball valve, but I’ve unfortunately forgotten to close the ball valve when running the water pump before. The good thing is after flooding things once, I think I’ll definitely remember to double check it from now on.

[DJ18]

We left everything open for a few days with the tank full and water pump on. sure enough, another slow leak at one of the Tees is obvious. there are some 2x4s screwed to the floor, I suspect to keep things stored under there from snagging or bumping the plumbing. The Avion is so well designed, I can't help but think a lot of this water line has been replaced and not positioned correctly. I'll be looking for pictures of other's plumbing now.

[KYAvion]

PEX is the ideal replacement. In the meantime, however, you can cut out the tee and use vinyl braided tubing, a pex tee, and hose clamps to do a repair. Just size the vinyl braided tubing so it is just a fraction larger than the grey polybutylene tubing, and use a little Vaseline if needed to help slide the braided tubing over top the old stuff.