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Pressure relief valve won’t discharge water

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seized123
seized123 Member Posts: 297
edited September 2023 in Oil Heating
When I pull the lever on the Watts PRV shown below (30psi, Weil-McLain oil boiler has MAWP of 50 psi) nothing happens. I know that when these things leak it’s time to replace them; this isn’t leaking but I assume this non-discharge of water when testing means I have to replace it? The boiler gauge read about 12 psi but I increased the pressure to about 20 via the feed valve and still no water when lever pulled. If it makes a difference this boiler has only been run for a few minutes in past couple of weeks - but I figure that shouldn’t make a diff, since I am seeing water pressure in there. It would be a pain to replace this valve and have the same thing happen, but since I’m seeing pressure I can’t imagine what this no water discharge would be a symptom of other than a bad valve.

If I have to replace it, what do I have to do before/after replacement to drain/reduce pressure/purge/refill the boiler? Hopefully in the photos you can see my various shutoff valves: one before the feed/pressure reducing valve where water is provided to the whole system, one ball valve for each zone on the same side as feed valve - the side the water comes back from each zone - and one ball valve at the zone valves on the other side where water goes to the zones. (And of course the drain valve at the bottom of the boiler.)

I was thinking, maybe wrongly, that I would close the main supply feed and all the zone ball valves on both sides so I don’t drain water from the zones, open the drain valve at the bottom enough to relieve pressure, close it and replace valve? And what then? Just refill using feed valve until I see 12 psi? Would I have to worry about air, or would that Hy-Vent on top of the boiler take care of that?


Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,607
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    Maybe you have a defective gage. it is very unlikely if you open the valve no water would come out unless the lever on the valve is broken. Put a temporary gauge on the boiler drain (open the drain and see if you have water their) but gauge on with a regular gauge and hoxes thread adapter or you can buy gauges with a hose adapter already on it. Shut the burner off until you get this resolved you don't want to melt the boiler
  • seized123
    seized123 Member Posts: 297
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    @EBEBRATT-Ed thanks I will do exactly that.
  • 109A_5
    109A_5 Member Posts: 1,387
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    Hello @seized123,
    Maybe air was trapped under the PRV and now that pipe is full of rust and junk sealing off the valve from the boiler.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    SuperTech
  • Jamie Hall
    Jamie Hall Member Posts: 23,419
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    One way or another, a pressure relief valve which won't discharge water needs to be fixed, right away.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Larry WeingartenSuperTechGGrossMikeAmann
  • seized123
    seized123 Member Posts: 297
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    Okay @109A_5, so sounds like I should remove the valve and pipes to take a look maybe before buying a new valve. On that note, what do I do in terms of draining/purging etc, as in questions in 2nd and 3rd paragraphs of original post?
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    Please fix the flue pipe. Draft regulator is installed incorrectly for oil. Being your dropping the pressure to change the relief valve, maybe fix the feed/expansion tank fiasco.

    There was an error rendering this rich post.

    SuperTechrealliveplumber
  • WMno57
    WMno57 Member Posts: 1,330
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    I think I see a water softener in you pictures. Don't refill with softened water. Softened water is bad for boilers. Hard water is the lesser of two evils.
    I DIY.
  • psb75
    psb75 Member Posts: 843
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    I don't see any backflow preventer.
  • seized123
    seized123 Member Posts: 297
    edited September 2023
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    Okay, lots of stuff. Just so I know, @STEVEusaPA, why is the feed/expansion tank a fiasco? Is it just the rust or is it in the wrong place or should be configured differently? Good idea to fix it while pressures’s down, please tell me exactly what’s bad so I can do that.


    Yes, I now know the draft regulator is on the wrong place (should go on the side, I think). It’s just that there’s so much going on with this stuff I’ve been leaving that for later.


    Good catch @WMno57, it’s not a water softener, it’s a neutralizer, for pH. We still have very hard water.


    @psb75 regarding the check valve, is this thing (in picture below) a check valve?


    Lastly, please tell me how to depressurize and repressurize. Close all ball valves from feed and to and from zones, isolating the boiler, and then open the drain valve? Purge somehow after refilling boiler from feed when done? 


    Before I do anything else, I’m going to go get a pressure gauge for the drain valve as per @EBEBRATT-Ed to see if there’s really pressure.


    RonnieJ
  • seized123
    seized123 Member Posts: 297
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    Update: BTW I'm no longer waiting to fix the barometric damper, ordering stuff now, including new 8" inch Field Controls RC because the one on there is 7" and I learned reading the NORA manual and also calling Field Controls that they suggest 8" damper on 7" pipe (have to use a reducer) with a chimney over 16 feet, which mine definitely is.

    24 gauge stuff is hard to find around here.

    Still would like to hear why the feed valve and expansion tank are wrong, sounds pretty important...
  • Jamie Hall
    Jamie Hall Member Posts: 23,419
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    There's a difference between wrong -- as in not ideal pracctice -- and wrong, as in it doesn't work. In your case it's the former. Ideally, one has the pressure regulating valve feeding the system at or very close to the expansion tank, and the main circulating pump pumping away from the tank, spaced a foot or two away on the piping. Yours isn't quite that way, but if the pump is running OK and the pressure is reasonably constant, not to worry.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • HomerJSmith
    HomerJSmith Member Posts: 2,467
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    Do you have an electric dryer in that basement that's venting into the room?
  • seized123
    seized123 Member Posts: 297
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    Thanks @Jamie Hall. The feed valve looks mighty close to the expansion tank, I don't see how I could get it any closer unless I move that thing that I think might be a check valve? In the below photo I include the circulator, it's less than two feet from the expansion tank (mounted on the vertical pipe that elbows down to vertical after the tank). This is all on the side that feeds the boiler. The diagram in the WM manual (see below) looks to me to be pretty much the way it's set up (with the circulator in what they call an alternate position). But I would change something if you think it would make it better.
  • seized123
    seized123 Member Posts: 297
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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,037
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    If you are going to take the time to drain the boiler in order to replace the relief valve, and therefore make other corrections to your system, You might want to make it easy on yourself for air elimination and purging. What type of radiators do you have? Standing Cast Iron? Copper tube baseboard? Panel radiators? Convectors? In order to get your system to operate at its peak efficiency, you want to eliminate any air in the system. By using the principles of Boyle's law and Henry's law regarding air dissolved in water, You want to pump away from the expansion tank with the circulator on the supply side of the boiler. That will make the boiler's built-in air-scoop the most efficient way to remove air from this system.

    Is there room to move the circulator pump to the supply side of the boiler? You may want to look into isolation flanges for the new circulator location. Circulator flanges with built in valves https://www.supplyhouse.com/Webstone-H-40405-1-1-4-Threaded-Isolator-Flange

    See the attached files. This is the least amount of change for the most amount of advantage. Some may suggest more invasive piping, I'm suggesting this as a lowest cost to get the most bang for your buck.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    MikeAmann
  • seized123
    seized123 Member Posts: 297
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    @HomerJSmith I do have an electric dryer ducted to outside. Interesting question, why do you ask?

    @EdTheHeaterMan those pictures should hang in a museum. Thanks!!!

    There might not be room for the circulator on the other side, see photo below. But if not, I could still put in the back flow preventer and the ball valves. (I have well water, but I assume a backflow preventer would still be a good idea?)

    I have copper tube baseboard. So let’s say I have the parts and I’m going to do these changes now. Would I close the ball valves to the zones (supply and return, so 8 valves total, since I have four zones) as well as the one that feeds the feed valve, and then just open the drain at the bottom of the boiler, which I guess would just drain some water out of the boiler itself, or at least relieve pressure? Or do I drain the zones too (that’d be a lot of water). I’ve never drained or purged anything that wasn’t beer, and I’m sure the answer’s obvious to you, but none of this is obvious to me.


  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,607
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    Leave the piping as is unless something is leaking, and you have to fix it. You're pumping away from the expansion tank as it is now piped. No need to move the circulator to the supply side.

    That's Weil McLain's alternate location for the circ pump and it's fine.

    The only drawback is it puts the relief valve on the discharge side of the pump. But in a low resistance system it does not matter
    hot_rod
  • Jamie Hall
    Jamie Hall Member Posts: 23,419
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    I completely agree with @EBEBRATT-Ed on this.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,037
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    Since you do not have room on the supply side, you should leave the piping as is.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • mattmia2
    mattmia2 Member Posts: 9,734
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    I'm betting those elbows between the relief valve and the boiler are clogged, either need to clean them out with a rid or screwdriver or replace them if that is the case. Unless the relief valve is very new it should be replaced while you have it apart even if it isn't clogged/stuck.
  • seized123
    seized123 Member Posts: 297
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    Good advice.
  • WMno57
    WMno57 Member Posts: 1,330
    edited September 2023
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    It's possible nothing comes out when you pull the lever on the relief valve because the black steel outlet pipe has rusted closed. A dribbling relief valve could have rusted up the outlet.
    If so, take the outlet pipe apart, ream it, and see if you can get the existing valve to both flow and seat by exercising it with the lever.
    Part of annual maintenance.
    edit, I see Matt had the same thought. OK, now you have to do an inspection for Matt and I. I'll check back in five minutes :)

    I DIY.
  • seized123
    seized123 Member Posts: 297
    edited September 2023
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    Lots of great info, though still nobody’s told me how to drain/relieve pressure, so unless someone tells me otherwise I’ll shut all zone and feed valves, isolating the boiler and open the drain. Using my secret weapon, almost total ignorance, I reason (having no experience) that what will happen when I open the drain valve at the bottom is that the closed valves will be like the finger on top of a water-filled straw: some water will come out and pressure will be relieved but not all the water will come out. But then it seems to me if I disconnect the PRV at the top of the boiler, the finger has come off the straw and the boiler will empty, or nearly. What to do after all is hooked up again I have no idea; just fill via feed valve until 15 psi pressure? Do I have to worry about air?  Comments welcome, if none I’ll just have to do it and deal with the consequences.

    I have to say though if I understand @WMno57 right, I could first check the piping on the outside of the PRV in case that’s clogged, and for that I wouldn’t have to depressurize. Great idea, be nice if that’s the problem. If not though I’d have to check the inner elbow etc. like @mattmia2 says.

    Draining?…
  • mattmia2
    mattmia2 Member Posts: 9,734
    edited September 2023
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    Close all the valves to the system and the supply to the prv, open a drain somewhere in the isolated part until there is no pressure then take apart the piping to the relief valve.

    If any of the valves aren't fully open, mark where they are because they may have been set that way to balance the system.

    If you only take the relief valve and ells out you may only need to re-open the supply to the prv and let the boiler refill and vent through the automatic vent and relief valve, if it air locks one or more zones you might have to purge or bleed them until you start flow.

    It looks like it is set up to purge at the returns.
  • seized123
    seized123 Member Posts: 297
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    Thanks @mattmia2 just what I needed to know. Yes, purge at returns. Interesting about balancing, I think all ball valves are wide open.

    Gotta go back now and check the thread about the lady getting the new oil tank: real time drama! Look forward to the movie.
  • seized123
    seized123 Member Posts: 297
    edited September 2023
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    I haven’t removed anything yet because I noticed according to the date code on the relief valve (itself a replacement I believe) it’s from 2005, so I figure I should replace it no matter what. I simply ordered what was on there, a Watts 174a for $122. Then (after ordering it, of course) I thought to look in a WM manual, and their recommended replacement valve (branded WM like the boiler) is a mere $38. It would still be worth it $-wise for me to get the cheaper one and pay the return shipping for the WM one, but is there some reason the Watts would be worth my paying 3 times as much? Photos below.


  • mattmia2
    mattmia2 Member Posts: 9,734
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    It is just a higher capacity, can be used on a boiler with a larger firing rate. Probably what whoever replaced it had on their truck. Make sure the pipe sizes and gender match up or get the appropriate adapter.
  • WMno57
    WMno57 Member Posts: 1,330
    edited September 2023
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    You can take apart the expensive one with a tamper resistant torx bit. Or you can break off the tamper pin with a pin punch and use a regular torx bit. Guessing they used tamper resistant bolts for a reason.
    I DIY.
  • seized123
    seized123 Member Posts: 297
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    mattmia2 said:
    Probably whoever replaced it had on their truck.
    What I was thinking. Probably got charged 3x the other price plus markup too -  although my plumber was very honest and fair, and it did last a long time.

    @WMno57 I probably won’t take it apart unless I’m really curious. It’s so old I’ll definite replace it.
  • HomerJSmith
    HomerJSmith Member Posts: 2,467
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    The expensive one has a rubber diaphragm that separates the discharge boiler water from the valve's spring.
  • seized123
    seized123 Member Posts: 297
    edited September 2023
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    Does that make using the expensive one worth it? In all the things I’m trying to do to this poor old boiler I’ve been going expensive but better, but I wonder if it’s worth it here? I now have both valves coming (!), so I have a choice. I’ll return one along with some other knucklehead misorders.
  • seized123
    seized123 Member Posts: 297
    edited September 2023
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    Well @EBEBRATT-Ed, I did what you said and hooked up a water pressure gauge to the drain, opened the drain and gauge said zero (while the gauge on the boiler said 20 psi). Then I opened the feed valve until the new water gauge said 20 (boiler said 30) and pulled the lever on the relief valve (it did resist a little, I had to crack it slightly) and: water! Case closed, I just didn’t have pressure (boiler’s been shut down for weeks) the boiler gauge is defective, relief valve’s good.

    But wait! After I let the lever back down the relief valve kept discharging water until pressure went down to zero. So: broken relief valve after all? But it wasn’t leaking water back when the boiler was running (it’s been shut down for a couple weeks). And now when I open the supply valve the relief lets out water even when the lever’s down, which it never did, until pressure goes to zero. (If it matters, when it initially discharged the water looked sludgy.) Not only that, the relief valve itself is dripping somewhere at a connection, which was not happening before.

    I guess I might as well replace the relief valve since it’s so old and see what happens.

    But hey, when the pressure goes to zero isn’t the feed valve supposed to open and fill it up? That’s not happening. I’m going to turn off the ball valve to the feed valve so it doesn’t decide to fill the boiler and now the relief will let it out. Very confusing.

    I just shut all the zone ball valves too because it seems to me that the relief could drip all water out of the system via gravity.

    Ideas? Maybe the relief valve was sludged up and defective at the same time so the defect/leak didn’t show until I both restored pressure to the system and tested it? In other words, sludged enough not to let water through unless there was both pressure and an opened lever, which when there was both opened up the floodgates?

    And shouldn’t my feed regulator valve automatically open to supply water when boiler pressure’s zero? Replace that too?
  • WMno57
    WMno57 Member Posts: 1,330
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    I keep the water to my hot water boiler valved off all the time. I do check the pressure occasionally, and usually add a little water once per heating season.
    This would not work for a steam boiler.
    Try exercising the PRV and water supply valve to see if you can get them to work.
    I DIY.
  • WMno57
    WMno57 Member Posts: 1,330
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    And remember, your going to have to break some eggs to make an omelet.
    In other words, it's just an old boiler. Time to wrap up the planning and start wrenching.
    I DIY.
  • seized123
    seized123 Member Posts: 297
    edited September 2023
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    @WMno57 I’ll exercise them, but the feed valve might be 22 years old and the relief a couple years less so if I end up replacing them I won’t feel bad.

    Why do you off the boiler water, out of curiosity. I did do that while on vacation in winter, also shutting off whole house valve, wanting domestic water off but heat on while gone.

    Am I right that I should have heard that feed regulator feeding while pressure was down, is that how it’s supposed to work?
  • WMno57
    WMno57 Member Posts: 1,330
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    seized123 said:

    Why do you off the boiler water, out of curiosity

    Several reasons. I bypass my water softener when adding water. Boiler should have been plumbed to hard water, but that occurred before my ownership. Some day maybe I'll re plumb the boiler supply.
    I like to know how much water or air my hydronic system is loosing. I think most of it is loss of air from the air over water tank (absorbing into the water, then migrating to the single second floor radiator). Some of the radiator valve stems have green deposits, so possible losses there. I like looking at my tridicator. I'm rather proud of it as you can see from my forum picture!
    No Low Water Cut Off (LWCO). I'm on a well and we have electrical outages. Dry firing an empty boiler is preferable to having the water off for a while, then come back on and feed an empty red hot boiler. BOOM!
    I could spend 5 figures on a new boiler. It would be more efficient. It might be less reliable.
    I DIY.
  • Dave Carpentier
    Dave Carpentier Member Posts: 594
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    Would that boiler be too old to have a pre-purge to get the flue air moving before it sparks up ?
    30+ yrs in telecom outside plant.
    Currently in building maintenance.