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Pressure Reducing valves

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Dirk Wright
Dirk Wright Member Posts: 142
in THE MAIN WALL
Thanks for all your responses. You've been very helpful.

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  • Dirk Wright
    Dirk Wright Member Posts: 142


    I just bought a pressure reducing valve, and in the instructions, they require a shutoff valve upstream of the water supply and they require that the valve be shut off during operation of the hydronic system. So, if the shutoff valve is located immediately upstream of the reducing valve, how does the reducing valve regulate the pressure in the closed hydronic system if the shutoff valve is off? Does the job of regulating the pressure transfer to the expansion tank once the system is filled?
  • Bill Glynn
    Bill Glynn Member Posts: 3


    What is the PRV doing in the system (other than reducing pressure) If it's part of a make-up water train then put the valve in for service and leave it open.


    For make-up water you need in this order:

    1. Shut-off valve
    2. Back-flo preventer
    3. PRV

    That's it!

    Remember, 99% of PRV's that I have used is: Turn the screw "IN" to "IN"crease the pressure!
  • Dirk Wright
    Dirk Wright Member Posts: 142


    Thanks. The directions specifically state to close it. I was just wondering why. They state it is to protect from uncontrolled flooding in case of a leak. The boiler is supposed to shut off if the water level gets too low.
  • R. Kalia_8
    R. Kalia_8 Member Posts: 54


    It is certainly reasonable that the valve be left closed. Open the valve, fill the system through the pressure-reducing valve, close it. If the pressure drops and ultimately the boiler shuts down due to low water cutoff, you have a problem that should be fixed.

    If you leave the valve open when the system is leaky, you hide the problem, causing a more serious problem in future due to continuous introduction of oxygenated water.
  • Bill Glynn
    Bill Glynn Member Posts: 3


    Very good point, if you don't moniter the amount of water usage for the system. I don't know your application, but I would put in a seperate water meter for the fill of the system. This will allow you to know if you have a leak, but still keep the heat on.
  • brucewo1b
    brucewo1b Member Posts: 638
    Swimming in houses

    The reason for leaving the valve off is that if you go away on vacation for two weeks and burst a second floor pipe how much water damage do you want done to your home, a couple of gallons from the burst pipe that trickles out or the amount that can run at 12 psi through a 1/2 inch pipe at city water pressure for two weeks?
    Most people I know leave the valve on however the mfr doesn't want a lawsuit because you left and didn't find that broken pipe for 2 weeks.
    Don't think it can't happen I have seen it more than once.

    Bruce
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