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Help identifying a part (Any help is appreciated)

Good morning everyone!

Someone came out to service the boiler today. The wife mentioned that the water bill is higher than expected while the boiler is running (old boiler, but have only owned the home a little over a year). The service guy took a look and said that there was a valve that needed to be replaced, but that the part isn't made anymore. He wanted to red tag the machine, but she refused to sign anything since the boiler works, it's just inefficiently using water. He wouldn't tell her the name of the part, or anything identifying about it aside from pointing to it. To me, this screams that they just want to push us to replace. After all, we're relying on them for the assessment. We cannot afford to get a new boiler/heater right now and they're refusing to do any future service on it. As a result, I'm hoping you all can help me identify the part so that i can try finding it on my own. I've attached some pictures for you all.

The part reads "Thrush Relief Valve". Above that, it says "30 lbs" and below it says what appears to be "No. 7'
I'm not certain on the year of the boiler, but it is a National Boiler (National Radiator Corp), Series 2 (it could be a Series 3), size 2-A06.

If you have any questions, drop them down below and I'll do my best. Thank you all in advance!


  • BDR529
    BDR529 Member Posts: 269
    Really? Hope the tech reported it to the fire dept.
    JUGHNE Member Posts: 10,581
    Where do the pipes go to that are connected to the device?
    Are there more than 3?

    Back up and take more pictures so we see all of the piping.

    It might be a combo pressure fill valve and pressure relief valve.
    It is an oldie.
    HVACNUT Member Posts: 5,032
    That's just a real old 30 psi relief valve. It should have been replaced a long time ago. To be fair to the contractor, with a system that old, if something breaks because he breathed on it the wrong way, it turns into a can of worms pretty quick. And then who's left holding the stick? When a boiler is held together with retort cement, it's time to replace. It would be my first warning sign if I walked into that equipment room.
  • Steamhead
    Steamhead Member Posts: 15,995
    I think they just used the furnace ("retort") cement to seal the doors. Yes, it's an older boiler, but it's built like a tank. Still, we don't want to over-pressurize it.

    It should be possible to pipe in a new safety valve somewhere on or around the boiler. A knowledgeable pro should not have any trouble doing so.

    However, if water usage is an issue, I'd check to see if the expansion tank has the proper air cushion. That safety valve might just be doing its job.

    @OldBoilerHelpNeeded , where are you located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • pecmsg
    pecmsg Member Posts: 3,889
    Normally I would say get a 2nd, 3rd or 4Th opinion but from the looks of it replace that antique before you loose all heat!
    JUGHNE Member Posts: 10,581
    I see now that the right side has a cap on it.
    Bottom is the drain, seeing the pvc pipe added could mean it was a dripper and the drain pipe took it to a floor drain or sink perhaps.

    Your boiler does not continually use water, it is filled and reuses the same water over and over to move heat.

    If this valve is dripping it needs replaced. It is a very common part.
    As said above you may have an expansion tank problem which causes the drip.
    Also, some will not want to put a wrench on this for fear of old pipes breaking. Many of us have worked on worse piping and lived thru it.

    More pictures including your expansion tank, it is probably hanging near the ceiling, would get more attention here.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 5,652
    Replace the relief valve with a Watts 335 and a reducing elbow 1/2" x 3/4" That will be the lowest cost relief valve.

    @Steamhead has the right idea. Not everybody has $$$ set aside for a new modern boiler. And that old coal conversion has some life left in her. I have vacuum cleaned many of them over the years. To keep the combustion gasses from leaking out or room air from leaking in (and cooling down the heat exchange process) it is standard operating procedure to seal the door with furnace cement or "Stick-tite". In a perfect world I would recommend new equipment, however I sometimes find that some of these old cast iron gals only use 200 gallons of oil a year. How do you justify spending over $5000.00 to replace a working heater that will save them 50% of 200 gallons? They need to replace it when it cost too much to operate or when it breaks down beyond repair.

    That said, you want it to be safe with a proper relief valve.and if the relief valve is actually working, doing its job, You need to find out why the pressure is rising to 30PSI and fix that.

    @OldBoilerHelpNeeded, you need to find an oil heat dealer with experience on these old cast iron babies. I'm sure there will be someone in your area with enough smarts to figure this out, and be glad to sell you fuel. Assuming you have an oil burner somewhere below those 2 cast iron doors.

    Just know that one pipe repair can lead to another and another and another. that heater is over 70 years old
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • unclejohn
    unclejohn Member Posts: 1,830
    Take a picture of the pressure gauge as well.
    EBEBRATT-Ed Member Posts: 13,454
    Why is everyone so quick to immediately condem the boiler?
    JUGHNE Member Posts: 10,581
    edited November 2019
    Ed, because it is "outdated", and Ed we will be too sometime soon.......this is a word my 18 year old grandson uses talking about my 1984 van and my Fax machine. ;)

    New term now Ed: some people are "ageist".....not PC BTW.
  • Steamhead
    Steamhead Member Posts: 15,995
    Here is another thread on an older boiler, showing a few upgrades we sometimes do:

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service