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Thread: Should PRV be before iirrigation system and house? Or just house?

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    Engineer garyl53's Avatar
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    Default Should PRV be before iirrigation system and house? Or just house?

    Hi,
    I have a failed PRV and I will be replacing it this weekend. I will also be adding some ball valvles to make this all easier if this happens again. I noticed that the supply to the irrigation system is on the house side (low pressure side) of the PRV. My last house had the irrigation supply on the supply side (higher pressure side). My street supply pressure is about 100psi and the house will be set about 60 psi. What is the correct way of doing this?
    Thanks,
    Gary

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    While the higher pressure might be nice for watering, 80 pounds is often considered the max for 'normal' domestic use, so you might have to fight with the inspector and, you'll likely be replacing the washers and seals more often to keep them from leaking at the higher pressures.
    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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    Engineer garyl53's Avatar
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    So 60psi should be plenty for the irrigation system assuming I have the flow needed?

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    DIY Senior Member asktom's Avatar
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    Your whole irrigation system would have to be sized to know how it would work, includiing specifications of the manufacturers of the heads and valves. I would be tempted to use two regulators so you can adjust the two systems optimumly and separately. That said, if what you had worked before then it will work again.

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    Engineer garyl53's Avatar
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    OK thanks. I will leave it as is and see how it works. If I need higher pressure for the irrigation I can always add a seperate regulator later.

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    DIY Member TWEAK's Avatar
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    Hi Gary,

    If the sprinklers were providing good coverage (full head to head coverage is the way to design a sprinkler system) before the failure, there is no reason to assume that they won't work well after you repair it.

    It's not really possible to determine in general if any sprinkler system will work properly because we have no way to know if your piping system is properly sized and layed out, and also if you have a proper number of heads on each zone. If you have too small of piping, a poor layout with long runs or long branches of many series-connected heads, lots of bends, etc, or too many heads in a zone then the system may not work well.

    60-70 psi is a pretty typical static water service pressure. Assuming (and all it can be is an assumption) that your system is properly designed (for a good tutorial on sprinkler system design, visit Jess Stryker's web pages on irrigation systems) there is no reason why it won't work fine.

    Again, history is your best guide. If the sprinklers were working well before your PRV failed, they should continue working after you replace the PRV.

    One thing that you probably know but I'll mention anyway is that you should make absolutely sure you get FULL PORT ball valves. At high flow rates, the pressure drop associated with small bore valves (especially if you have a couple of them) can cost you quite a lot. Full port valves cost a little more but are well worth it.

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    Plumber jimbo's Avatar
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    A lot of properties I see with the sprinkler system tied off ahead of the PRV. But if your street pressure is higher than 80, 85 to 110 range, and you use the el cheapo control valves, such as the Orbits from HD or whatever, you will have lots of problems with those. If you go with the higher pressure , get commercial quality rainbird models, or similar.

  8. #8
    Engineer garyl53's Avatar
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    Thanks for the additional info. Irrigation was working fine before so I will leave it the same. Thanks for the tip on the FULL PORT ball valves, I wasn't aware that several types existed.
    Gary

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    Moderator & Master Plumber hj's Avatar
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    I set my PRVs at 75-80 psi, but you will probably not notice any difference at 60 psi, just as you would not likely see any changes in performance with full port valves as opposed to non-full port ones, unless the opening was severely restricted. The only place a full port is REALLY needed, in a residence, is when we have to put a "flow stopper" in the pipe to install the valve. Then the full port is needed so we can extract it after the valve is soldered on.

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    Engineer garyl53's Avatar
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    Hi,
    I just thought I would let you know that I installed the new PRV this weekend and everything is working just fine, including the irrigation. I set it at about 60psi and that is more than enough to handle the irrigation the way it is designed at my home.
    Thanks again for the information and help,
    G

  11. #11
    Moderator & Master Plumber hj's Avatar
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    One consideration as to WHERE the irrigation system is connected, is that I connect it before the house shut off valve, since many residents in this area are absent for extended time periods in the summer. They like to turn off the water to the house without affecting the pool water filler or the irrigation system. Since the PRV is usually after the house valve, that means that the irrigation is usually before the PRV, unless there are two valves to control the house supply. One before the PRV and one after the irrigation connection.

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