Bypass feature of a Pressure reducing Valve?

Question

Some states require an expansion tank installed with a pressure reducing valve with or without a bypass feature. California State code is not specific on wether this creates a closed system. I would like to know if a Pressure reducing valve creates a closed system even with a bypass feature? A pressure reducing valve is installed on the main water line from the supply to the home to reduce water pressure below 80PSI. It is similar to a check valve until the thermal expansion of heated water reaches the supply pressure to activate a bypass feature. Can you look on the body of the pressure reducing valve and be able to determine if it has a bypass feature?

Answer 1

A bypass feature on a PRV is designed to protect whatever it is serving by allowing water to go back through it if the pressure in the system after it gets too high. Many of the PRVs manufactured today come with this feature. Every PRV should have a tag on it, and you can check with the manufacturer to see if it has this feature.

This does not constitute a closed system. A closed system needs a certified backflow prevention device in order to qualify as a fully closed-system.

Answer 2

You don't want to rely on a pressure reducing valve to act as a bypass, even if it has one built in (which I have never heard of). Why? Well, because you want an independent way of reducing the pressure inside your tank should your pressure reducing valve fail or if something causes your tank to overheat. How can a pressure reducing valve, which is upstream and relatively cool, handle thermal expansion? It can't.

I think this is why I've never heard of a pressure reducing valve having any bypass feature. Some of the pressure reducing valves have a vacuum breaker built in, but never a overpressure bypass feature.