Originally Posted by woliners
... I noticed that there is another pressure relief valve at the pipe exit underneath the camper body.
What's that all about. Do I really need 2 valves in series like that ... ?
next question: Are these "special" valves or can you get them anywhere? ...
The relief valve on the water heater is designed to pop open at a certain pressure OR
a certain temperature. The settings are usually 150 psig or 210 degF. Plumbing code mandates that valve has to be there.
My '67 Overlander has a pressure relief valve on the cold water line (probably the other relief valve you noticed). At first, I considered it's presence the mark of superior design .i.e. one could do without it, but on occasion it might be useful.
But, I noticed that valve dribbles a little bit when water is heating (heating water raises the pressure in the line). So the valve serves a constantly useful purpose.
Airstream used a cold water relief valve rated to vent at (IIRC) 60 psig. Hardware store models are rated at 90 psig. InlandRV sells an Airstream-approved cold-water replacement.
I think you should keep both relief valves.