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prv

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zvalve
zvalve Member Posts: 83
Hvacnut and others
Here is a picture of my boiler and the left most copper pipe has no shutoff on it so if I need to replace the prv, which appears to be leaking from the gasket just under the top, will water come spewing out on the side opposite the supply side of the prv. Then do I need to drain the entire system to replace the prv? Is the prv supposed to be oriented vertically? Could a bad expansion tank cause the prv to leak?

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  • Henry
    Henry Member Posts: 998
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    You have one valve before the circulator. Do you have a valve after the expansion tank? If so, you would not have to drain the system. If we do not have a valve, we freeze the pipe and install one. The PRV are installed horizontaly.The expansion tank would not damage the PRV.
  • HVACNUT
    HVACNUT Member Posts: 5,865
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    There's a ball valve on one branch of the split return above the circ. Is there a valve on the other branch?
    If so,
    Shut off the switch.
    Close the return valves.
    Close the valve to the PRV.
    Close the supply valves if any.
    Tighten the cap on the auto air vent.
    Drain the boiler from the boiler drain. Can't see it in the pic, but it's going to be at the same level as the return elbow going into the boiler.
    ONLY drain to 0 pressure. As soon as the water stops flowing, quickly close the valve.
    Have tephlon tape ready.
    Using 2 wrenches, remove the union side of the PRV.
    Using 2 wrenches, remove the other side of the PRV and use a rag and Philips head and plug the hole.
    Put tephlon on the threads.
    Remove rag and install the new PRV.
    Reverse all steps.
    Start the boiler and check the heat.
    How old is the auto vent? When the pressure is off the boiler, it would be preventive maintenance to replace it now. Taco 400, 1/8".
  • zvalve
    zvalve Member Posts: 83
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    Hvacnut and Henry thank you so much for your input and hvacnut there is no valve on the the far left branch of the return so what can I do? FReeze it as henry said and install one? How do you freeze it?
  • Alan Welch
    Alan Welch Member Posts: 270
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    Don't think you have enough room to spin off the p.r.v. or spin on a new one , you may need to disconnect the circulator bolts to get enough room to spin off. And need to drain the boiler at that point.
  • HVACNUT
    HVACNUT Member Posts: 5,865
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    Ooh, good catch @Alan Welch.
    Another idea down the pooper.
    @Zman. Are there valves on the suppy?
    Where are the purge stations?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,631
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    Maybe I am wrong but isn't that prv installed on the circulator pump inlet with the circ pumping into the boiler?? And is not the expansion tank installed on the supply so you have the circ pump installed between the prv and the expansion tank.

    not right
  • zvalve
    zvalve Member Posts: 83
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    EBEBratt
    2 returns and cold water supply>circulating pump>boiler>expansion tank>2 zones with thermostatically controlled valves>radiators>return.
    not right?
  • zvalve
    zvalve Member Posts: 83
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    As more heat is delivered during this cooler weather the prv stopped leaking. Only one valve on one return line, no valve after expansion tank except for two zone valves so if I want to remove prv I need to drain entire system so water doesn't come gushing out through return line with no valve. (refer to photo). Is it difficult to refill syem and bleed out air? I am a neophyte and need guidance.Yes! there may not be enough room to spin off prv but if its not leaking during heavier heating periods maybe I should postpone
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,631
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    The PRV outlet connection (water entering the boiler) must be under the same pressure as the expansion tank and should be piped in the same proximity (preferably to the same T) when connected to the system.

    I am surprised others have not picked up on this
  • JUGHNE
    JUGHNE Member Posts: 11,077
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    He could put a tee between the air separator and exp tank. Put a valve on the tee, then PRV could be serviced.
    OR just move the pump and PRV to the supply side of the boiler.
    Add valves as needed.

    Or if it is a budget issue; drain the system, remove the top from PRV, you may have enough room to spin it.

    Or: I am not familiar with this PRV, but are most of the moving parts connected to the top cap? If so just change the top and you have a new gasket. Rebuild in place so to speak.
    zvalve