PRV Questions

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by James, Sep 13, 2019 at 5:06 AM.

  1. James

    James New Member

    Joined:
    Friday
    Location:
    North Carolina
    Well the PRV to our home failed (pressue spiked to 160 psi in the house), so I searched and found the valve buried in our front yard, next to the water main.

    I wasn't comfortable changing it myself, so I called a plumber. After he looked at it, he suggested putting the valve in my garage, next to the main shut off valve. It is common in our neighborhood for the PRV to be in the garage, but for some reason our builder installed it in the front yard, so I said sure and he went ahead and installed it in the garage.

    After some thought (or maybe over-thinking), I wondered if that will now affect the life of the pipes between my water main and my garage (since they were running low pressure before, now they are seeing 160 psi all the time)? Should I be worried? Should I go ahead and replace the PRV in the original location, or was that just a poor location to begin with?

    Any help would be greatly appreciated.
     
  2. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    See what kind of pipe you have. If it is rated for 160 or more you are good. Normally pipe to the house would be rated for much more than 160.
     
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  4. James

    James New Member

    Joined:
    Friday
    Location:
    North Carolina
    Thank you. So, how do I tell the pressure rating of my pipe? I believe it is copper in the front yard, but my shut-off valve in the garage is blue plastic pipe.
     
  5. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    The blue pipe should be marked down the side. Wall thickness of copper will tell you the rating, but even thin wall should be rated higher than 160 PSI.
     
  6. Sylvan

    Sylvan Still learning

    Joined:
    Sep 23, 2004
    Occupation:
    plumbing- - fire suppression
    Location:
    New York
    I would be very concerned with that kind of pressure in case a pipe or fitting lets go

    I normally reduce the incoming pressure to less than 80 and in most cases 40 PSI is enough pressure to even allow flushometers to operate properly

    Most IPS fittings and valve have a 125 rating "WOG"

    With that kind of pressure boiler safety or relief valves will be spewing all the time water heaters T&P valves will remain open and erosion of ferrous and non ferrous metal piping will fail and the possibility of hydraulic shock is very likely

    Even 5 story building in NYC only require 60 PSI ( 5 stories x 12 feet )


    Figure a 5 story building let's figure it is 60 feet above ground level and you need 15 # at the upper most fixture you would add 6.5 feet more for the pressure requirement and another 10 feet as a fudge factor

    Total pressure requirement is based on 76.5 feet x .433 = 33 PSI (static pressure)

    Take the 33 PSI x 2.31 = 76.23 ft

    160 PSI x 2.31 your now able to elevate the water to 369.6 FEET HIGH

    EVEN fire hoses do not come close to these types of dangerous pressures

    Why would anyone need or want that kind of pressure?

    Even fire suppression systems in some residential buildings are less than 20 PSI at the uppermost head and are code acceptable
     
    Last edited: Sep 13, 2019 at 7:49 AM
  7. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    He doesn't need that high pressure. It is just what he has to deal with. Very common for some cities to supply really high pressure like that. With a good PRV the house will only see 50-60 PSI if that is the PRV setting. Only the pipe before the PRV needs to be rated for high pressure.
     
  8. James

    James New Member

    Joined:
    Friday
    Location:
    North Carolina
    Thank you valveman! Really appreciate the responses.
     
  9. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    I think the inside pipe needs to be able to take 150/160 psi also. That could occur if the thermal expansion tank fails, for example.
     
  10. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    I wouldn't count on the pressure expansion tank. With a PRV setting of 60 I would use a pressure relief valve after that set at about 75 PSI in case the PRV fails.
     
  11. James

    James New Member

    Joined:
    Friday
    Location:
    North Carolina
    I guess the piping in our house did handle the failure, at least for the 24 hours it took to fix the PRV. I mainly noticed the problem because some of my bathroom sink cartridges starting leaking and when anyone flushed the toilet, it sounded like a jet taking off in the house. I imagine over a longer time period, more things would have failed, but the pipes probably wouldn't burst (joint failures maybe?).
     
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