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Boiler T&P valve drips

My T&P has been dripping on a 4 year old boiler.  The system pressure says 12-13psi when cool.  The extrol 60 expansion tank has 12-13 psi, and the supply valve to my prv is closed.  This started after I had the boiler cleaned and checked.  The tech said my boiler psi was a little high, and he let pressure out of my expansion tank, I later recharged it, because when the system psi was 0, so was the tank.



So, can the T&P bad after 4 years, or should I be looking at something else.  I am new to the forum, and not knowledgeable about boiler systems.



Thanks for you help. 

Comments

  • ChrisJ
    ChrisJ Member Posts: 11,985
    edited November 2013
    Pressure

    I'm a homeowner not a pro and I know very little about hot water systems.



    However my understanding is the compression tank should be precharged when not connected to the system. I'm not sure but I recall a 14 psi precharge if the system runs at 12 psi. I could be way off on this though as I said I know little about hot water systems. I do recall it having to do with the static pressure in the system though and I believe the correct precharge is VERY important so don't just go off of my 14 psi.



    If I was you, I would take the tank off, make sure the bladder is good and precharge with the correct amount of pressure. Next I would replace the T&P because its probably just leaking. I believe it is very common for them to leak especially if they have been tested / opened after a long time of sitting.



    I know this post is kind of like the blind leading the blind but maybe it'll put your mind at rest.



    Hopefully a pro can help you out.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604
    Leaky relief valve

    If the system pressure is remaining at 13-14 PSI and the valve still leaks, the valve is bad, or has dirt on the valve seat causing it to leak.  You can try raising the manual release lever to flush out the valve and see if it helps.



    The valve is designed to release at 30 PSI and should not leak at all before that pressure is reached.
  • chicagoed
    chicagoed Member Posts: 4
    leaky relief

    Thanks for your quick response.  I'm a novice to this boiler, so I may ask dump questions.  Can you tell me what the psi should be when the boiler is heating?  The T&P is only 4 years old,  but from what you say, I should change it.  Is there some reason why iy would go bad so soon?





    Thanks
  • Weezbo
    Weezbo Member Posts: 6,232
    edited November 2013
    the thing about this is ,

    the tank works better with air in it.

    best way , is to take the tank off charge it to like 28 psi and let it settle down read it again let air out to say 12 psi.

    in situ , a blowout gun will bump it up about 3 psi.

    Weezbo.
  • ChrisJ
    ChrisJ Member Posts: 11,985
    Heating pressure

    As far as I know the pressure in the system should be the same weather hot or cold. If it changes, I would say the tank is defective.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604
    Pressure increase with temp

    As the system heats up the pressure will increase because the volume of water contained within it increases with temperature.  The expansion tank provides a place to store the additional volume, but because the volume of air must decrease, it is compressed and  the pressure rises.



    At max temp, the pressure may increase to 20 or 25 PSI, but must remain below 30 PSI to prevent the relief valve from opening.



    Precharging the tank allows it to contain more air volume at the static pressure, so it can accept more water without exceeding the 30 PSI limit.
  • chicagoed
    chicagoed Member Posts: 4
    precharge expansion tank

    I brought the system down to 0 psi, and charged the expansion tank to 12psi, if I increase the psi, does that mean the tank can hold more water or less water?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    edited November 2013
    Less

    It's referred to as acceptance volume. Increasing the air charge decreases the tanks acceptance volume. Also, you should fill the system to 1/2 psi per vertical foot of system elevation above the boiler pressure gage, and add 5 PSI to that number. Typical minimum is 12 PSI



    Lastly, T&P valves are normally only on DHW systems. If it is a true boiler, then it only needs pressure protection from the relief valve, so it's not a T&P valve, but a pressure only relief valve. Usually indicated on the rating tag on the device.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • chicagoed
    chicagoed Member Posts: 4
    Thanks

    I would like to thank all of you who responded to my questions, and for educating me on hotwater boilers, and terminology associated with them.  I feel that the more I understand how things work the better off I am.  Thanks again 
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    We're here to help...

    and you can help the fine owners of this site by purchasing a book from thieir extensive book sotre. That pays the bills around here.



    Happy Thanksgivakkuh. Or is it Mozzlegobble... :-)



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • bill_105
    bill_105 Member Posts: 429
    Mozzlegobble?

    Oh yea, that's the last words spoken to a Jewish turkey before it's executed and thrown in the oven;)

    Now in keeping with the site topic, has anyone ever done a CO reading next to a Menorah?

    Also, here is the hot tip, it's Green Bay minus 6.

    Now go eat everything in sight! Happy Everything!
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