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Locknivar NKC199N Combi boiler steady dripping from pressure outlet pipe

dseltzdseltz Posts: 8Member
My Locknivar noble nkc 199 boiler is steadily leaking from pressure outlet pipe. Pressure looks low though (10psi). Any ides what could be going wrong?


  • STEVEusaPASTEVEusaPA Posts: 3,334Member
    Has it released recently?
    Double check pressure with a known proper working pressure gauge.
    If pressure is good, you'll have to replace it.
  • JUGHNEJUGHNE Posts: 6,039Member
    Your expansion tank could also be waterlogged.
    Just depress the tank schrader valve, maybe under a blue cap, just for a split second. Do you get air or water?
  • dseltzdseltz Posts: 8Member
    Well after overflowing a bucked overnight and then filled up half a bucket in about 3 hours but now it has stopped. Pressure value still says ~ 10 psi. What do you mean “has it released recently”? Don’t see a Schroeder valve on my expansion tank.

    We do have hard water here by the way.
  • JUGHNEJUGHNE Posts: 6,039Member
    The Schroeder valve should be on the bottom.
    I see you are fortunate to have an isolation valve above the tank.
    If you shut off the boiler, shut off the cold water supply, close that isolation valve and unscrew the tank just enough to release any water pressure in it.
    The tank should then feel empty, if not when removed it needs replaced.
    To sum it up: with the tank disconnected, laying on the floor it should have 12-15 PSI of air in it. If water logged it is heavier than you imagine. Don't damage the Schroeder valve.
  • dseltzdseltz Posts: 8Member
    OK, got it. Thanks. Right now the dripping is still stopped. If it starts again I’ll follow your steps. Thanks!
  • JUGHNEJUGHNE Posts: 6,039Member
    You may need more than that 10PSI (if correct) for your system to operate correctly.
    Some service people will never test/flush your pop off valve for fear of it not reseating and dribbling forever.

    I test all I come across at least once a year. Lift the lever and let it run for a couple of gallons. You may get a shot of nasty looking water with the first operation. Then snap it shut hard to make sure it is reseated and not leaking. This also tests the refill valve to bring the pressure back up as needed.

    Of course I have a spare close at hand.
    If done every year then this keeps the seat clear and seldom do you have to replace them.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 6,047Member

    If you isolate and unscrew the expansion tank be careful. If the tank is light it is probably be ok.. If the tank is defective it could be waterlogged and could be full of water and will be broken toes!!!!
  • IronmanIronman Posts: 5,221Member
    If that's a combi, there are two separate relief valves: one on the boiler side and one on the domestic side. To which one are you referring?
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • bob eckbob eck Posts: 892Member
    Noble combi boiler comes with a 50 PSI yes I said 50 PSI boiler relief valve from the factory all three size BTU inputs of 110K, 150K and 199K. Check the tag on your boiler relief valve. Is it a 50 PSI boiler relief valve. The installing contractor could have switched the 50 PSI relief valve for a 30 PSI boiler relief valve that is the normal PSI on most residential boilers in America.
    We have been selling the Noble combi boiler since they came out and I told my Lochinvar rep BJ Terroni to ask Lochinvar if they could put a red sticker on the side of the combi boiler near where the relief valve is mounted so contractor notice the relief valve needs to be 50 PSI. As far as I know Lochinvar has not put a sticker on the combi boiler saying 50 PSI boiler relief valve needed.
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