Pressure reducing valve impact on flow rate?

Reply

  #1  
Old 11-25-13, 12:58 PM
Member
Thread Starter
Join Date: Nov 2013
Posts: 26
Received 0 Votes on 0 Posts
Pressure reducing valve impact on flow rate?

I have a pressure reducing valve installed at the entry point if my 3/4" water main which drops the pressure from 120psi to 80psi.

My current renovation will be adding many bathrooms such that I could have 8 showers going at one time in a worst case. Will the pressure reducing valve adjust as flow increases and demand for water increases, or will it simply restrict flow below the capacity of the 120psi available? If I go to the full 120 psi most manifolds don't have the specs to handle more than 100psi, so I could not use the full pressure from the street on most home run manifolds.

Does anyone have suggestions?
 
Sponsored Links
  #2  
Old 11-25-13, 01:30 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,894
Received 25 Votes on 23 Posts
Psi and your Gpm are two different things...

80 psi is the max pressure to be run in residential homes by code AFAIK... Do not increase unless you want to start blowing joints on the water pipes...

Find out how many GPM your main supplys... You may need a bigger meter or increase pipe size from 3/4 to 1".....
 
  #3  
Old 11-25-13, 02:05 PM
Forum Topic Moderator
Join Date: Sep 2005
Location: USA
Posts: 4,719
Received 29 Votes on 28 Posts
As Mike was saying, the PRV will limit pressure, but does not significantly limit flow rate (GPM). My first thought was that you could use 2 or 3 PRVs in parallel, each connecting to two or 3 bathrooms. But as I thought through it, it wouldn't matter. You have great pressure up to your meter, so you'll have good pressure throughout your house even with a few fixtures in use. But a 3/4" main will only provide so much volume... and will eventually tap out with multiple 2GPM showers going at once.

Time how long it takes to fill a 5 gallon bucket from an outside faucet. Time the number of seconds it takes to fill, divide by 5 (gallons) and multiply by 60 (seconds). That's your Gallons Per Minute (GPM). A standard low-flow shower head uses 2 - 2.5 GPM.
 
  #4  
Old 11-25-13, 02:27 PM
Banned. Rule And/Or Policy Violation
Join Date: Apr 2013
Location: USA
Posts: 4,297
Received 0 Votes on 0 Posts
How about a large pressure tank to even out the flows by adding more storage capacity?
 
  #5  
Old 11-25-13, 02:59 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,967
Received 2 Votes on 2 Posts
Still going to be limited in GPM by the size of pipe. Pressure is pressure. I would reduce MY pressure even closer to the "norm" of 60-65 psi, but you are within parameters as you are.
 
  #6  
Old 11-25-13, 07:43 PM
Member
Thread Starter
Join Date: Nov 2013
Posts: 26
Received 0 Votes on 0 Posts
Thank you for your answers. This is helpful. Now that I understand this, let me try to refocus the question. Psi and gpm are different measurements. However, there is a relationship between psi and gpm in a given system. If a higher psi is introduced to a given system gpm will increase.

So, my question is that will a pressure reducer restrict the gpm available at 120 psi, or will it adjust. Because as the flow increases, pressure is relieved from the system, and the pressure reducing valve will respond and let more water through. As fixtures are shut off, the valve will restrict more. Is that the way of it or will the pressure reducing valve decrease available gpm from the 120 psi available?
 
  #7  
Old 11-25-13, 07:53 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 17,894
Received 25 Votes on 23 Posts
Yes it maintains pressure..

But your total GPM say 8 showers x 2.5 gpm = 20 gpm may exceed the GPM your supplied with...

Read here. This will save me some typing....


Water Pressure Reducing Valves - Water Conservation - Learn About - Watts
 
  #8  
Old 11-26-13, 04:20 AM
Member
Thread Starter
Join Date: Nov 2013
Posts: 26
Received 0 Votes on 0 Posts
Thanks. That helped. It appears that a parallel installation with 10psi difference in the setting between valves will deliver better capacity. I'll look into that.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


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