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

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    DIY Member philtrap's Avatar
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    Question 120 PSI fresh water from town - Going to install a PRV

    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

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    Forum Admin, Expert Plumber Terry's Avatar
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    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

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    Retired Defense Industry Engineer jadnashua's Avatar
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    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member dj2's Avatar
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    Install a separate PRV for the sprinkler system, and set it at 75.
    We do it all the time.

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by dj2 View Post
    Install a separate PRV for the sprinkler system, and set it at 75.
    We do it all the time.


    That would work better, especially if you want to use both at the same time.
    Theory only works perfect in a vacuum.

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    In the Trades Gary Swart's Avatar
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    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.

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    DIY Member philtrap's Avatar
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    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???

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by philtrap View Post
    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???

    Yes..........
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

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    DIY Member philtrap's Avatar
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    Quote Originally Posted by DonL View Post
    Yes..........

    Thanks!!!!!!

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    Sprinkler Guy Wet_Boots's Avatar
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    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.

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    DIY Senior Member dj2's Avatar
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    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.

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by dj2 View Post
    BTW, since January 1, 2013, all PRVs sold in CA must be "lead free". But that's another issue.

    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.
    Theory only works perfect in a vacuum.

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    DIY Senior Member dj2's Avatar
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    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?

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    DIY Member philtrap's Avatar
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    Wet_boots, A question for ya...

    Quote Originally Posted by Wet_Boots View Post
    ... if the installer designed the system to depend on the high flow the 120 psi supply would provide...

    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.

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by dj2 View Post
    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?

    lol


    Them old pipes must be why everyone is going Nuts.

    Kind of late to fix them now.
    Theory only works perfect in a vacuum.

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