120 PSI fresh water from town - Going to install a PRV

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by philtrap, Sep 7, 2013.

  1. philtrap

    philtrap New Member

    Messages:
    66
    Location:
    Long Island, NY
    Folks,

    I have a 50 year old home with no fresh water pressure reducing valves (PRV) installed. I found this out after my garden hoses kept blowing and I checked the pressure which is at 120 psi at all the outside spigots and the sinks inside where I could thread on the pressure tester. I've tested the pressure at all times and it's always 120 psi or close to it. There is no PRV after the meter and I'm not sure if there is a faulty one the town installed underground somewhere before the meter (which is in my basement), but I doubt there is one. Anyway, a quick question...

    I have a lawn sprinkler system that works great. If I reduce the incoming pressure from 120 psi to 50 PSI (the factor set for the PRV) right after the meter, do you think the sprinklers will work the same or will I have to make adjustments to them? The PRV I'm planing on installing would be before the sprinkler system just after the meter... I could install the PRV after the sprinkler system since it's teed off after the meter on it's own line, but there is one spigot on that line too and the hoses on that would keep blistering and blowing if it wasn't regulated.


    Thanks in advance
  2. Terry

    Terry Administrator Staff Member

    Messages:
    14,911
    Location:
    Bothell, Washington
    If you have any valves on the irrigation, the 120 psi will be too much for them too.
    It may not be a bad idea to have a PRV for the home and one for the irrigation.
    Code requires pressure reduction for anything over 80 PSI
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,924
    Location:
    New England
    While the PRVs do come preset from the factory, that doesn't mean that they are not adjustable. Residential plumbing fixtures are designed with the 80psi in mind, and have a decent margin of protection when it gets higher, but it's best not to test them on a regular basis!

    Keep in mind that adding a PRV requires adding an expansion tank to account for the fact that makes the system 'closed', and when you heat water, when it expands, it needs a place to go.
  4. dj2

    dj2 Member

    Messages:
    409
    Location:
    California
    Install a separate PRV for the sprinkler system, and set it at 75.
    We do it all the time.
  5. DonL

    DonL Banned

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    3,956
    Location:
    Houston, TX


    That would work better, especially if you want to use both at the same time.
  6. Gary Swart

    Gary Swart In the Trades

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    7,334
    Location:
    Yakima WA
    Even a lower pressure would not be a bad idea for the house supply. Mine is set a 50 psi and that seems to be quiet enough for me. Expansion tank is a must.
  7. philtrap

    philtrap New Member

    Messages:
    66
    Location:
    Long Island, NY
    I have an expansion tank right before the hot water heater on the cold water side. Is this the one you guys say is a must???
  8. DonL

    DonL Banned

    Messages:
    3,956
    Location:
    Houston, TX

    Yes..........
  9. philtrap

    philtrap New Member

    Messages:
    66
    Location:
    Long Island, NY

    Thanks!!!!!!
  10. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    The lawn sprinkler system complicates matters, if the installer designed the system to depend on the high flow the 120 psi supply would provide. There are sprinkler systems that end up requiring extensive reworking, if something is installed in the supply line that significantly cuts pressure and flow.

    A standard PRV comes with a high insertion loss. Charts that display friction loss through a PRV almost always base the performance curve on their being a minimum of 50 psi pressure reduction through the PRV. Any standard PRV that is only partially opened (when you don't have the full 50 psi loss set up) will have much more pressure loss than the charts would suggest.

    What can work best for regulating lawn sprinkler system pressure is pressure-regulating master valve, which doesn't kill the pressure (beyond your adjustment of the output setting) and flow in a sprinkler system. Most every major sprinkler manufacturer has one or more of these in their product offerings, and they often cost less than a standard brass PRV.
  11. dj2

    dj2 Member

    Messages:
    409
    Location:
    California
    Wet_Boots,

    I live in an area where the street water pressure is 150 in the flat areas and more than that in the rolling hills.

    Folks who don't have a PRV in their sprinkler system, experience leaks.

    I own a rental on a hill, where I have to replace the PRVs every 5-6 years. Last week I replaced 2 of them for customers. I install Wilkins regulators only, not plastic crap.

    BTW, since January 1, 2013, all PRVs sold in CA must be "lead free". But that's another issue.
  12. DonL

    DonL Banned

    Messages:
    3,956
    Location:
    Houston, TX

    They did the same BS for Foot Valves.


    Time will tell... The way people on Earth are acting, there may not be much time left.
  13. dj2

    dj2 Member

    Messages:
    409
    Location:
    California
    I don't mind making my home "lead free" or "99% lead free". But when I get my water from 80 year old galvanized city pipes...where's the logic?
  14. philtrap

    philtrap New Member

    Messages:
    66
    Location:
    Long Island, NY
    Wet_boots, A question for ya...


    Would a sprinkler installer design it at 120psi? Isn't that too high for the heads and the zone valves? I'm just asking and I'm not sure much design went into the irrigation system other than the guy saying I have enough pressure and he'll put the heads in "these" spots to make full coverage. BTY, I tested the biggest zone today after installing the PRV which I adjusted to 60psi and it seemed to work fine. They didn't spray as far, but they still hit all the grass. Most of them overlap some so I think it should be fine running at 60psi.
  15. DonL

    DonL Banned

    Messages:
    3,956
    Location:
    Houston, TX

    lol


    Them old pipes must be why everyone is going Nuts.

    Kind of late to fix them now.
  16. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    Sight unseen, there isn't any way to know for sure. To be able to cut in a PRV into an existing sprinkler system and not have it suffer catastrophic loss of performance requires that the existing sprinkler system have pressures in the zones that are 20 psi more than required. Basically, every head would be over-pressured to the point of generating visible misting.

    Installers typically aren't leaving any available flow under-utilized. There is real value in getting the watering done in a minimum of time. I would never, ever, assume the ability exists to cut in a standard PRV on any existing sprinkler system.

    Understand that the supply pressure is never getting to the sprinkler heads. By the time water flows through the meter and supply line, into the sprinkler system and through a backflow preventer, the 120 psi you measured with the system not running drops below 100 psi. In the homes I deal with, having water meters in the basement, the pressure loss in the supply line to the house is a big factor.

    When I do see a genuine need to reduce sprinkler zone pressure beyond what a flow control on each zone valve can provide, then it is the regulating master valve I employ, because it alone is capable of sustaining full flows in the sprinkler system.
  17. DonL

    DonL Banned

    Messages:
    3,956
    Location:
    Houston, TX

    For a House that old I would bet it was not designed for 120psi.

    Flow and volume is more important than pressure, Because as soon as the heads start spraying the pressure drops, then you want volume and a pressure of 60 psi is fine.


    Have Fun.
  18. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    The age of the sprinkler system figures into things as well. Since modern design practices call for more sprinkler heads placed closer together, with each head spraying onto the next head down the line, such systems are much more tolerant of a pressure loss than are older systems, that counted on a head spraying the 40 feet it was intended to, and not a few feet less.

    120 psi is not higher in pressure than any sprinkler zone valve's pressure rating. Most of them are rated 150 psi, and top models can have 200 psi ratings. In practical terms, 120 psi is around the point where you would have a PRV in the system supply (like a Wilkins BR-4 set at 80 psi)

    What a PRV does more than anything, for a sprinkler system, is to cut down on water hammer when zone valves close. Quieter plumbing makes for happier customers.
  19. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,334
    Location:
    Yakima WA
    No where in this discussion do I see any mention of back flow prevention. It seems everything just tees off the line from the meter. I realize the problem in point is the excess pressure, but unless you have a back flow prevention device for the irrigation line, you should look into this.
  20. philtrap

    philtrap New Member

    Messages:
    66
    Location:
    Long Island, NY
    Gary - Thanks... The irrigation system does have a Watts back flow preventer valve.
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