Watts 25aubz3 - prv question


  #1  
Old 01-22-23, 11:35 AM
P
Member
Thread Starter
Join Date: Dec 2022
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
Watts 25aubz3 - prv question

I understand that this valve doesn,t have a built in check valve thus allowing water to back up upstream in the system. If this is the case does that eliminate the need for an expansion tank.
 
  #2  
Old 01-22-23, 05:27 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 71,675
Received 3,333 Upvotes on 2,992 Posts
Welcome to the forms.

Yes.... you are correct BUT an hydronic pressure tank is set to roughly 12-15 psi. If you didn't have that pressure tank.... your boiler would have to increase pressure to over 40 psi to be able to get pushed back into the water supply. Your boiler T & P valve releases at 30 psi. Way before the system pressure would get pushed back into the water supply line.

In other words... a pressure tank is still needed.


Watts 25AUB specs - pdf
 
  #3  
Old 01-22-23, 06:29 PM
D
Member
Join Date: Apr 2014
Location: us
Posts: 1,557
Received 99 Upvotes on 93 Posts
Pressure reducing valves are "one way" and do now allow reverse flow so check valves are generally not used. They supply water pressure at typically 12 psi and automatically replenish any that is lost.

https://www.supplyhouse.com/Watts-00...eaded-F-Outlet

In a closed hot water heating system, as temperature of “non compressible” water changes, flexible bladders in expansion tanks maintain set pressure. https://www.youtube.com/watch?v=S2HVSogYELM

Without expansion tanks pressure relief valve may open to release water: https://www.supplyhouse.com/Pressure...alves-17144000
 
  #4  
Old 01-22-23, 06:33 PM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 3,435
Received 129 Upvotes on 121 Posts
There may be a little confusion here with this PRV. This one is used to reduce house water pressure and not a hot water heating system. This particular valve has a range of 25-75 psi to reduce street pressure in the home if you happen to live in a home with excessively high pressure of 100 lbs or more which could damage your fixtures.

An expansion tank in most cases is not necessary but if you find your T&P dripping due to thermal expansion after a while when everything is off an expansion tank could help, but not the same tank that would be required on a heating system. A tank maid for potable water and can handle street pressure water would be needed.

Hope this helps a little.
 
  #5  
Old 01-22-23, 09:43 PM
D
Member
Join Date: Apr 2014
Location: us
Posts: 1,557
Received 99 Upvotes on 93 Posts
Regardless of application PRV " Pressure Reducing Valves are "one way" and do now allow reverse flow so check valves are generally not used.

The most common PRV failure is leaking valve seats that results in pressure rising above setting., so a check valve to prevent back flow is useless
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: