# Pressure Reducing Valves



## Scott K (Oct 12, 2008)

A quick question for you - Do Pressure reducing valves (e.g. Watts 25-75 models, etc.) allow backflow due to thermal expansion from the HWT, back into the City supply?


----------



## A Good Plumber (Jun 18, 2008)

Not likely, but possible if the pressure downstream was to build in excess of the incoming pressure.


----------



## DUNBAR PLUMBING (Sep 11, 2008)

Scott K said:


> A quick question for you - Do Pressure reducing valves (e.g. Watts 25-75 models, etc.) allow backflow due to thermal expansion from the HWT, back into the City supply?


 
N55's has a built-in thermal expansion bypass that's supposed to open at 135psi only if the main line pressure is lesser. 



Most, if not all PRV's are backflow devices by default. If you install a PRV, it's automatic for an expansion tank or device in connection with dealing with thermal expansion. T&PRV does not count.


The 25AUB34 is one of the most reliable PRV's out there, but I use the N55's because they are shorter, and I get them with 3/4" sweat unions so installation and replacement is a cinch.


----------



## rocksteady (Oct 8, 2008)

we use wilkins prv's exclusively and i know the #70 has a bypass. i was told it opens at 150psi but i don't see how that would help if the t&p pops at the same pressure. they could be set to bypass at 135psi too, would make more sence. either way, they do have a bypass for thermal expansion.







paul


----------



## pzmember (Sep 20, 2008)

the watts 25 aub does thats the 25- 75 psi range.


----------

