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Safety Valve on Boiler leaks steady stream of hot water. What is wrong?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Don2222, Sep 17, 2010.

  1. Don2222

    Don2222 Minister of Fire

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    Salem NH
    Hello

    My friend has a very old Gentleman Janitor vintage oil Boiler with tankless coil and baseboard heat. The safety valve just started leaking a steady stream of hot water.

    What is wrong? What is the best way to fix it?

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  2. in hot water

    in hot water New Member

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    it could be the tankless coil has sprung a leak and is allowing the city water pressure into the boiler. turn off the water supply to the tankless coil and see if it stops the relief.

    hr
  3. ohbie1

    ohbie1 Member

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    I have a couple of suggestions from personal exp.

    Since the boiler is old, the spring on it could be weak and not applying the necessary pressure. However you can do the following:

    1. Check the pressure gauge on the boiler and make sure it reads quite a bit less than the safety valve tag. The safety valve probably reads 25 or 30. The boiler pressure gauge should read maybe 12 to 20, not more. If the gauge is higher you have a problem that is not the safety valve.

    2. If the gauge pressure is lower, then you have a safety valve problem. Put a bucket under the safety valve pipe and pull up the lever on the safety valve a couple of times letting it snap back (use a glove, the water can be hot). If you are lucky the leak will stop, meaning that the valve was not seated properly possibly because of sediment. This is not LIKELY to work, but it's worth a shot, because if it does not work you will have to replace the valve (a much more time consuming job).
  4. btuser

    btuser Minister of Fire

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    Yep. What they said. Don't cap it, because then it will blow up.
  5. sgrenier35

    sgrenier35 Member

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    Check the expansion tank and make sure it is not water logged
  6. btuser

    btuser Minister of Fire

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    Sometimes they just go bad. Other times its because you've got other problems like the expansion tank. I think just about every time I've tested an old pressure safety vavlve I've ended up replacing it, but I'm lucky that way.
  7. benjamin

    benjamin Minister of Fire

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    Could also be the fill valve or pressure reducing valve is leaking, if the pressure is higher than it should be and the pressure relief valve is functioning correctly.
  8. vvvv

    vvvv New Member

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  9. glhenry56

    glhenry56 New Member

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    I was just writing to someone about my Tarm boiler experience, which last winter included an overheat/overpressure/relief valve failure event. And I suddenly realized that I have an obligation to pass along my experience and learning, because things may have turned out much more poorly. Looks like this is a good forum for that.

    While burning wood in my mid '80's vintage Tarm 502 one Saturday last winter, I inadvertently left my lower door cracked open. The boiler water temp and pressure continued to build well above 200° and actually exceeded the 30 PSI relief setting of my safety relief valve by the time my wife noticed something wrong. After realizing what had caused the problem, I first closed the door and opened up a couple of hot water valves in the house to help drop the boiler temp (my boiler has a domestic hot water coil). I then made sure the relief valve blowoff piping was directed well away from me, protected myself from a possible steam burn, and manually lifted the relief lever. Pretty scary result as the ~260° water instantly flashed off and filled my small boiler room with steam, but I felt at that point that it was better than risking a disastrous pressure part failure. The learning I got from that sobering event was:

    • Test the relief valve annually (or more often if that is what the boiler or relief valve manufacturer recommends). I hadn’t exercised the lever in several years, partly because I figured “it may not re-seat tightly, and if so I’ll have to buy and install a replacementâ€. Sometimes a man can be too cheap for his own good! "Penny-wise and pound foolish" is another way to put it. Those relief valves aren't free, but they're a hell of a lot cheaper than hospital stays or funerals.
    • Do not install the relief valve horizontally, as it lends itself to deposition around the valve disk and seat which can cause the disk to seize. That is exactly what happened in my case, and because I hadn’t exercised it regularly, it didn’t open when needed. My boiler came with a horizontally mounted relief valve, and in fact, my Tarm owners manual actually has a photograph of the valve improperly installed. Perhaps that wasn’t considered a problem back when the boiler was made, but I’m now fully on board with the vertical installation that Watts recommends. In fact, I'll attach a photo of the attached tag on my Watts relief valve that spells it out quite clearly. And since I'm not an "expert", here's a link to a Bell&Gosset; page on the topic: http://www.bellgossett.com/homeowners/gpart1.htm

    Of course, I wouldn't have subjected my heating system to an overheat/overpressure situation had I made certain the door was tightly latched when I had loaded it up, and I have thought about installing a "door ajar" warning light on the boiler. I would be interested in reading about devices others have used to assist feeble-minded folks like me. But stuff like that is why relief valves were invented and regulations like the ASME Low Pressure Heating Boiler Code were written.

    Attached Files:

  10. coal boiler

    coal boiler New Member

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    dump zone could be to small to bring heat down after aquastat turns on dump zone dump zone should be half of what boiler holds mine is 85 gal dump is 40gal had it smaller and pressue valve would open plus install expantion tank for pressure variations and shocks from zones opening and shutting
  11. peakbagger

    peakbagger Minister of Fire

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    I second the suggestion on the expansion tank. Ninety percent of the time, a slow leak is a sign of a waterlogged tank. If the pressure gauge is any good on the boiler (they frequent arent) chekc the pressure, if its up much over 15 psi or up near the rating of the releif valve its time for a tank.
  12. bpirger

    bpirger Minister of Fire

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    Where's the fellow who was posting about heating storage routinely to higher temps (like 230+) instead of adding more volume.....That water flashing to steam must be something to experience...hopefully in extremely small volumes. :)

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