Boiler Pressure/Bleeding Air


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Old 12-07-09, 09:20 AM
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Pressure out of control - tagpat

I have a similar problem. I have a gas boiler radiator heating system. Pressure rises in my system and eventually the pressure relief valve opens to relieve the pressure if I don't drain water periodically. I have a 60+ year old furnace and the expansion tank is the large metal tank directly above the boiler.

As a work around, I have turned off the water supply to system, so that no new water is drawn into the system to add to the overall pressure in the system. This has kept the pressure in my system more stable and doesn't require me to drain any water. Maybe you could try this for your problem.

I believe this problem is caused by air getting into the system, perhaps through a leak in the expansion tank. My pipes and radiators gurgle even with the water supply cut off and no amount of bleeding is doing me any good. System heats just fine, including all radiators, but it's probably not as efficient as it should be and I'm afraid I'm going to damage my circulator pump. Would appreciate any thoughts.
 

Last edited by NJT; 12-07-09 at 06:06 PM. Reason: lack of any continuity is due to moving hijacked thread
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Old 12-07-09, 09:31 AM
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Originally Posted by tagpats View Post
I have a similar problem. I believe this problem is caused by air getting into the system, perhaps through a leak in the expansion tank.
If closing the shut-off to the automatic fill valve stabilized the pressure, that points to the automatic fill valve leaking past its seat. Replace it, but in the meantime, keep the isolation valve shut.

Assuming that you have positive pressure throughout your system when the boiler is cold, air can't leak in. But gurgling may indeed point to air in your system. Are you getting heat from all your radiators? If your Airtrol fittings are installed correctly, air in the system should eventially wind up in the expansion tank.
 
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Old 12-07-09, 09:34 AM
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A fiill valve is the same thing as a reducing valve correct? I replaced this valve thinking it was allowing water to leak into the system and boosting my pressure, but there was no improvement to my problem. I have turned off the shutoff between the street and this reducing valve many and drained down my system many times and the only way I can keep the pressure remaining relatively stable once the system is fully heated is to keep the shutoff turned off so that no water can come in from the street.

If I have done what you suggested, is there anything else besides air getting into my system that I should consider? I was thinking maybe a pin hole had developed at the top of the tank or something. It would seem that if I had a hole any place else, I would have noticed water, but maye not if it is is a tiny leak.

I'm a real novice plumber and am just trying to nurse things along until I replace my system in the next few months.
 
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Old 12-07-09, 09:41 AM
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I'm not sure I follow on the fill valve leaking past its seat. My stem is set up so that I have a pipe that brings water in from the street to my system. There is a shut off valve that I can close to block water from coming in. Next to that shutoff is a reducing valve that has a metal arm that I can lift to allow water to come into my system (if the shutoff next to it is not closed like it is now) and next to the reducing valve is my relief valve with a pipe that runs down to the floor to drain any overflow.

all of my radiators get warm and seem to be working well. my cold pressure is around 12 and my hot pressure is around 20, but i can play with these numbers depending on how much water i allow into the system or drain off when need be.
 
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Old 12-07-09, 10:18 AM
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Originally Posted by tagpats View Post
I'm not sure I follow on the fill valve leaking past its seat.
Yes, we are talking about the same thing here: fill valve = pressure reducing valve. There's more to it than just the fast-fill lever. It has a spring-loaded disk against a seat that automatically opens if the system pressure gets below the setpoint, say 12 psi. When it leaks past the seat, water trickles into boiler continuously, even when the system pressure is above the setpoint. (Your city water pressure is probably 50-60 psi.)

If closing the shut-off valve ahead of the fill valve (PRV) solves the problem, I think that points to a leaking fill valve. I can't explain why you still have the problem after replacing the fill valve.

What make and model is the repacement fill valve? Please post photos of your system - post on one of the freebie hosting sites, and link here.

20 psi for system when hot seems a bit high. What is the boiler temperature when hot? How old is the pressure gauge? - sometimes, over time, they can read high.
 
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Old 12-07-09, 11:05 AM
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Thanks for sticking with me on this. That makes sense to me too, but I guess moved past the fill valve as the cause when I replaced it and just assumed it had to be other issues if I was still experiencing the same problem after replacement. I'm using a Bell and Gossett model no. FB-38 set at 12psi. My gauges could certainly be wrong given the age of the system, but the temp reading is around 180-185. my cold psi right now is 14. Could my system just not be pressurized properly and it is somehow telling the valve to fill as a result, as opposed to the fill valve being faulty?

Besides replacing the fill valve again, is there a way for me to get my system working close to normal in the meantime by keeping the shutoff from the street closed? Either way, I'd like to start from scratch and make sure my expansion tank is set properly and my pressures are in normal ranges and maybe all my tinkering with adding and draining has created problems. I do have a shut off ahead of my expansion tank that i've used to drain my tank. Maybe I've introduced air into the system that way.

Finally, I've been told conflicting things about bleeding air out of the radiators. I was told by someone that the best way to do this is to open them when the system is cold and not running, but any time I do this water just drains out and there is no hissing of air being released. The only time I get spitting of air is when the system is fully heated and running. I was warned that doing it this way would let air in, but that didn't seem right to me.

I'll try to figure out how to post pictures. Really appreciate the help!
 
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Old 12-07-09, 11:45 AM
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Originally Posted by tagpats View Post
...I was told by someone that the best way to do this is to open them when the system is cold and not running, but any time I do this water just drains out and there is no hissing of air being released. The only time I get spitting of air is when the system is fully heated and running...
The system requires an air removal device that returns the air back to the expansion tank. With the bleeders spitting air and water the air is being pushed through the system. Just need to capture it and return it to the tank.

Al.
 
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Old 12-07-09, 12:21 PM
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yeah, sorry about that. i came to the forum to post basically the same questiona and was surprised to find his right at the top. thought he might have similar luck closing off his shut off from the street.

i assume my pump and configuation is correct, since the problem didn't present until recently, but i'm just not sure.
 
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Old 12-07-09, 12:24 PM
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short of this air removal system that i must not have, is there a proper way to bleed off of my radiators? i never noticed gurgling in my radiators until i developed this pressure building problem, and even though i've stabilized the pressure problem by closing the shut off valve, the air is my biggest issue now.
 
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Old 12-07-09, 02:02 PM
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The air probably got in with the fresh water. It has O2 dissolved in it which is now exiting the water as it heats up.

On a system with large volume pipes and radiators the air will usually collect at the high points. Say an upright CI rad. Once the air enters it just goes to the top and sits there waiting to be bled out.

On a system with smaller diameter pipes and/or a circulator that will really move the water & air through the system. There needs to be a device to capture and purge the air. In your case back to the compression tank.

A system with a bladder tank the air gets expelled completely out of the system.

Check your system where the compression tank is connected in. There should be a device such as an air scoop or inline air separator. A system as old as yours may instead have a separator built into the flow control valve or even a B&G AirTrol fitting in the boiler (at hot water feed to the radiators).

Al.
 
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Old 12-07-09, 02:20 PM
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Originally Posted by tagpats View Post
Besides replacing the fill valve again, is there a way for me to get my system working close to normal in the meantime by keeping the shutoff from the street closed?
Yes, that's exactly what you should do.

Tagpats thread is moved to here...
 

Last edited by NJT; 12-07-09 at 06:08 PM.
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Old 12-07-09, 03:05 PM
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Boiler Pressure/Bleeding Air

Thanks for the help with my questions from the the previous thread and sorry for the confusion with my piggybacking on the original post.

I closed the shut off before the expansion tank so that i could drain it completely. After doing that, I re-opened the shut off before the fill valve. Then I re-opened the shut off in front of the expansion tank and water moved into the tank and i could hear water passing through the fill valve filling up the system. It finally stopped filling and stabilized with the pressure at 22 cold. I drained it back down to 12 and it is now fully heated and running at about 18.

As a result of bringing in a load of freshly oxygenated city water, I'm gurgling as much as ever. I was not able to locate any sort of air release system other than a little bleeder on a hot water pipe connected to and above the pump just like the bleeders i have on all of my registers. Is there a definitive way to manually bleed the air or do i just live with the gurgle?
 
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Old 12-07-09, 03:49 PM
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Thanks for starting a new thread.

I seem to recall that you have a conventional steel expansion tank with Airtrol fittings? And didn't we establish that your PRV (fill valve) was leaking through? If so, then I thought the game-plan was to leave the shutoff valve ahead of the fill-valve closed to prevent leakage from the city water supply into the boiler system - but you have now reopened it?

If your system refilled to 22 psi cold, were you using the fast-fill lever (or bypass) or was the flow just automatically coming through the fill valve? If the latter, more confirmation that the fill valve is leaking past the seat.

Please clarify your situation. And please post pictures of your system.
 
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Old 12-07-09, 05:31 PM
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here's a link to some pictures.

Yfrog - Boiler Pictures

you are correct, i had it closed, but when i drained everything, i re-opened it just to see what the pressure would set itself to. i agree that this seems to confirm that my fill valve is faulty. either that or my perhpas my gauge is not correct and 22 is really 12. i had it set to auto, so it was just passing through on it's own and shut itself off at 22. i now have the shutoff in front of the fill valve turned off to keep water from getting into the system.

i guess i'll put a third valve in to see if that fixes the problem. once i do and assuming it is working correctly, are you able to confirm for me the proper way to bleed the air out of my radiators without investing in any new technology? i'm going to replace this system in the next several months, so i just want it quiet and as efficient as possible in the meantime. it's not that annoying to me, but when i have holiday guests and the system turns on at night, it's like a raging river gushign though my walls.
 
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Old 12-07-09, 05:35 PM
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and yes, i do have a conventional steel expansion tank, but i don't know what airtroll fittings are or where they would be located.
 
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Old 12-07-09, 06:16 PM
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Originally Posted by tagpats View Post
here's a link to some pictures.

Yfrog - Boiler Picturesi guess i'll put a third valve in to see if that fixes the problem. once i do and assuming it is working correctly, are you able to confirm for me the proper way to bleed the air out of my radiators without investing in any new technology?
No, don't add a third valve. Just leave the shutoff valve (the one with the red handwheel) closed as we previously discussed, and replace the automatic fill valve when you can.

If you've bled all the points that you can, several times over, just wait until the Airtrol fittings do their job, and divert air to the tank. Don't you have red fittings at the bottom of the tank and at the boiler outlet? They are B&G Airtrol fittings.

By any chance, you don't have a domestic hot water heater as part of your boiler, do you?

Why do you intend to replace the system? Because of air in the system? Replacing the boiler won't help with that.
 
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Old 12-07-09, 06:54 PM
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by third valve, i just meant that i have already repalced the fill valve once, so counting the original that i replaced and the one i have now, the new one will be my third fill valve.

i'm kind of caught in this bleeding loop. hopefully i'm not doing this wrong, but the only way i get air out is to bleed them when the system is hot and the pump is circulating. when i do this, my pressure drops from some loss of water and then i have to open back up the shutoff to bring in water to boost the pressure slightly. this in turns brings in more fresh water and air, which i don't really want to do. perhaps i'm better off either living with the air or living with the lower pressure associated with the bleed off of the registers and some loss of water and just keep it closed and not allow fresh water to come in at any point.

i don't see any airtrol fittings anywhere. here's some more pictures, including my pump and tank.

Yfrog - More Boiler Pics

my hot water heater is not connected to my furnace.

i'm remodeling my basement and want to get a new system that is more efficient and would like add a second zone so that my basement and upper part of my house are each on their own zone.

thanks again for trying to help me out.
 

Last edited by tagpats; 12-07-09 at 06:56 PM. Reason: corrected a misstatement
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Old 12-07-09, 07:22 PM
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If your system refilled to 22 psi cold, were you using the fast-fill lever (or bypass) or was the flow just automatically coming through the fill valve? If the latter, more confirmation that the fill valve is leaking past the seat.
OR that the gauge is toast... a bad gauge can send you round and round in circles... if 22 is really 12, and you dropped it to 12 on the gauge, then 12 on the gauge is really what? TWO?

CONFIRM THE PRESSURE GAUGE before you waste any more time or money.

Go to HD or Lowes and pick up a $10 gauge that lawn sprinkler dudes use. Screws onto a hose bib. On the way home, stop at a REAL supply store and pick up a 0-30 or 0-50 PSI gauge with the same thread as the 0-300 one on the one you bought. (might also try a swimming pool supply)

Replace the 0-300 with the 30 or 50 and screw it on a drain valve and open the valve. Read pressure.

That boiler... what memories! Believe me or not, I was working on that EXACT boiler... get this... when I was TEN YEARS OLD! It's _possible_ it is 60+, I don't know how long that model was in production, but the one I was 'in charge of' was installed in 1955. It had a different gas valve, but otherwise identical.

(I know you don't believe me, but it's true...)
 
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Old 12-07-09, 07:50 PM
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Thanks for merging the thread. I'm new to this forum thing and the etiquette was clearly lost on me. Appreciate the tip on checking the pressure. I'll give that a go.

My math was wrong. I double checked and my house was built in 1955. Except for this pressure problem and noise with the radiators, the system is flawless. It cranks out heat and has been totally dependable.

Appreciate you all being so patient and willing to take the time to educate me on a lot of fronts.

Makes sense that the gauge could be faulty after all this time, then again if it is and my fill valve is working properly, then I can't explain why when i leave the shutoff before the fill valve open, pressure in the system gradually increases with each cycle. Seems that there is considerable evidence that my valve is letting water through when it shouldn't be.
 
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Old 12-08-09, 02:35 PM
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No problem! We're all new sometime!

faulty after all this time, then again if it is and my fill valve is working properly, then I can't explain why when i leave the shutoff before the fill valve open, pressure in the system gradually increases with each cycle. Seems that there is considerable evidence that my valve is letting water through when it shouldn't be.
Yes, there is... but, don't get bit by the two-headed snake! It's VERY possible that you may actually have TWO problems.

What sometimes happens with new replacement valves is that the installers don't flush out the water line before putting the new valve in service, and since those lines don't flow a lot of water, they get bits of crud in them.

First thing is to verify the gauge.

Any unknowns can drive ya bonkers!
 
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Old 12-08-09, 04:24 PM
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What sometimes happens with new replacement valves is that the installers don't flush out the water line before putting the new valve in service, and since those lines don't flow a lot of water, they get bits of crud in them.
right you may be. the line was not flushed. helpful tip.
 

Last edited by NJT; 12-08-09 at 05:46 PM.
 

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