Leaky hot water heating system vent repairs - how to repair a leaky hot water air vent or bleeder valve: here we explain how to repair or replace both manual heating system air bleed valves and automatic float type air vents that are leaky.

Float type automatic vents on hot water heating systems are normally left "open" to automatically purge air from the system.

But a float vent that leaks water will stop working, may leak onto and damage equipment, and is often left "closed" or shut off as a temporary measure. And a manual air vent that is leaky or that no longer vents due to corrosion and clogging is not going to do the job when your heating system is airbound and radiators or baseboards are cold.

Air Bleed Valve Leak Repair: How to Inspect and fix or replace leaky float-type automatic or manual air bleeder valves (air vents):

These questions and answerss about how to troubleshoot and fix or replace air removal devices and air bleeder valves on hot water heating systems were posted originally at AIR BLEED VALVE LEAK REPAIR - be sure to see the advice given there.

Question: trouble getting the air out of an apparently air-bound heating system

We have a 2 zone hot water heating system that operates off of one thermostat. When calling for heat the 1st zone going to the 1st level of the home works good. The 2nd zone on the 2nd level has 6 baseboards and 3 seem to work good but 3 do not radiate heat at all.

Each one has a air bleeder on them and when I went to bleed the one off I got a little air but then got nothing, no water either.

Is it normal to have no pressure on them when not calling for heat or do I have an obstruction in the line such as frozen or some sort of debris? - K.C. 1/27/14

Reply:

I suggested looking for clogged air bleeders or for low system pressure.

See AIR BLEED VALVE LEAK REPAIR

and

See PRESSURE & TEMPERATURE SETTINGS, CONTROLS

Reader Follow-up:

The heating system is at my moms and I went over there yesterday to take a look at it and couldn't find a pressure gauge or not much of a place to put one with out taking apart some thing.

When I got there I had noticed that the water supply valve was shut coming from the water well going to the make up point of the hot water system and wasn't sure if that was suppose to be left open so I opened it and it sounded like it was taking some. Let me know if that is suppose to be left open or not or will it hurt something if I do.

When I did have it on and went to bleed the air I found quite a bit of air but when the air stopped I didn't get water and if I shut it and waited al little bit I could get some more air but no water.

Shouldn't there be enough pressure on the system to keep on forcing the air out until you get water so maybe the bladder is bad or I need to add some pressure to it somehow.

I did find out that it is a loop system and there is a 1" pipe looping along side the out side of the house between the floor and ceiling of the upper and lower level and pipes Ting off of it to the baseboards.

That is why we are still getting good heat at 2 baseboards at the beginning of the run and 1 at the end of the run but 3 in the middle you will get the one end of the pipe might be warm to hot but at the other end might be luke warm to cold.

Could there be a blockage in those pipes caused by sediment from the water? Or maybe the pump that moves the hot water isn't working right. Let me know your thought. Thanks for your time and help. - K.C. 1/28/2014

Reply:

I cannot give safe advice about operating the controls on a heating system I can't see - there are just too many unknowns.

If the water to the boiler was shut off it may be that the system has ONLY a manual water feed. If this is hot water heat, (not steam heat) and if the boiler is not leaky, it may rarely ever need water added

; if you pushed water in you may have overpressurized the boiler, which in turn can make the relief valves leak when the system heats up (another unsafe condition).

If on the other hand the boiler starting pressure was low, you might have addressed the original boiler pressure worry. But unless you bleed air until water comes out of the air bleeder valve, you have left air in the system - which can leave it air bound.

I think I would try forcing water into the system until I got water out at the air bleeder.

Then if I found I had too much pressure in the system, after bleeding out all the air one can always open a drain at the boiler to reduce the water pressure. (of course when you TOUCH an old part that nobody has touched for years it may break, leak or jam).

Watch out: for an old, not-working heating system that does not even seem to have normal safety controls and is in unknown condition, I don't think it's safe to keep fooling with it - you need to figure it's time to call a heating professional. We may try to offer some tips by email or online, but we are limited by your eyes - what you see and report.

Often a pro will be able to home in on the no-heat problem almost immediately (that's a benefit of having a lot of experience).

Reader Follow-up:

Thank you for your help. The resent info was some good advice.

I did shut the water valve off today and it didn't seem to set off any reliefs but I did notice that there was a bleeder on top of the bladder assembly and the cap was on and when I took it off it seem to bleed alot of air out and then seem to bleed it out in spurts like it was an automatic air bleeder

and when it did that I could hear water moving through the pipes better and went upstairs and was able to bleed air out of one of the baseboard until it came onto water which hadn't been able to do before and one of the shorter baseboards that she said hadn't been working in awhile was working now. sounds like slowly but surly things are starting to work.

I know it is hard to give info when not here looking at it but thanks for the info you have given.

At least it gave me some knowledge and will call some one in if can't get things working safely and normal.

Reply:

Sounds like progress. What's hard to determine from our conversation is to confirm that the system is air-bound (which I suspect) and whether you have found the bleed valves necessary to get that air out without having to call a heating service tech to force the air out of the system (using a pony pump at the boiler).

If you can keep bleeding air until water comes out at a bleeder that's what you want to do.

If you hear water moving through the pipes that was not moving before, you're making progress and we know the circulator must be working.

If you feel piping and it's hot for a ways from the boiler then is cold, that's probably where the air is blocking the system.

On 2018-06-20 by (mod) - automatic air vent on our boiler system is leaking.

I like to see a picture of the failed and also of any label or marking so that I can understand which model you have

On 2018-06-19 by Brian W.

The automatic air vent on our home heating boiler system is leaking. This air vent has two caps - one red and one black. It appears only the black cap valve is leaking. Why would my system have two valves on the air vent? Can I replace it with an air vent with only one valve?

On 2018-01-06 by (mod) - replace air eliminator or bleeder valve that can't be opened or can't be closed

I would consider replacing the valve

On 2018-01-06 by Dave P.

That looks like the valve I am dealing with. Thanks for the great research help. Any idea where I might locate more info/specs on this particular valve?

I suspect that if I can determine the size of the screw listed as part #24 on the drawing, I can make the repair rather simply. Unfortunately, the head on the screw is rather worn and soft, will not accept a screwdriver of any size, and there is not much to work with for the dremel or vice grips.

On 2018-01-05 by (mod) - if water comes out there is no air to vent at that location

If when you open an air bleeder on a radiator and WATER comes out then close the valve again - there is no air to be bled at that location.

If that radiator remains cold I suspect that there is an air blockage in piping ahead of the radiator or the radiator's inlet valve is closed or blocked, or, less likely, the radiator itself has so much rust at its water inlet that it's not accepting hot water.

On 2018-01-05 by (mod) - Examples of early air eliminators and air bleeder valves

Your original vent might be one of these

White, John H., and Rudolph T. Schoerner. "Automatic air valve." U.S. Patent 2,601,216 A, issued June 17, 1952, Assigned to Taco Heaters.

Or you might need to eliminate or add to that small street-ell that appears to be screwed into the radiator side to make your new vent more-easily accessible.

Also there are some radiator air vents using a larger knurled control knob that might be able to be operated in the space in your photos.

On 2018-01-05 by (mod) - Taco Coin Vent & Earlier Air Bleeding Valves

Dave,

Often we can turn a screw with damaged slot simply by using a larger screwdriver blade, occasionally after improving the slot using a Dremel tool cutting wheel, occasionally by gripping it with a small pair of Vise Grips.

If you cannot successfully open and close the air vent in question you can replace it. It looks as if the vent screws into a standard NPT 1/4" pipe elbow but I'm only guessing size from your photos. See AIR BLEED VALVE SOURCES at https://inspectapedia.com/heat/Air_Bleed_Valve_Sources.php

The procedure for replacing a bad air vent or coin vent or air bleeder valve is given in this article.

The difficulty I suspect is that the location of your air vent is very cramped, making selection of an air vent that can be operated from the side rather than from its top a desirable choice.

My first photo below is a traditional Taco type coin vent

I did not find the patent number you cited associated with Taco but below I show the original air vent patent by Joseph Balter who assigned this air vent patent to Taco Heaters Inc. in 1958.

There were, of course earlier versions of air bleeders and vents for steam and hot water radiators in the long history of modern heating systems, such as Simoneau's automatic air vent for hot water systems in 1943 - when I was a baby.

[Click to enlarge any image]

Simoneau's patent includes a nice explanation of the need to vent air from radiators and baseboards.

• Joseph, Balter. "Automatic vent valve." U.S. Patent 2,823,693, issued February 18, 1958. Assigned to Taco Heaters, Inc.,
  
  Excerpt: This invention relates to an automatically operating vent valve permitting the passage of air or other dry gases therethrough and closing off the passage of steam or other moist vapors when the latter reaches the valve, the steam or moist vapor condensing so as to cause the valve to shut off, such a valve being especially adaptable for use in a steam heating system, or other system requiring venting of air or gas.

• Simoneau, Charles B. "Automatic air vent valve for hot water systems." U.S. Patent 2,331,431, issued October 12, 1943.
  Excerpt:
  
  Various means, such as screw plugs, pet cocks, etc., are in common use for venting air from hot water heating systems, the plugs, cocks or other devices being opened and closed manually when it is deemed necessary to free the systems from pent up air. This often results in situations where there may be an accumulation of air which impedes circulation and reduces the ef ficiency of the systems.
  
  To remedy the unsatisfactory condition resulting from the presence of air, it is often necessary to call in a plumber, steam fitter or other service man to remove the air and return the system to normal condition. As is well known to those who are skilled in the art, when preparing a hot water heating system for operation, all parts are filled with water to a point above the highest radiator or the upper floor line.
  
  While the filling operation is going on, all radiator plugs, pet cocks, etc., where air might gather and make air pockets, are opened manuallyto vent air from the system.
  
  As the water rises to these open vents they are closed by hand as the appearance of the water at the vents shows that the air has been expelled, thus creating a theoretically perfect circulatory system.
  
  It is found in practice, however, that air pockets form in the radiators and continue to increase in area without the knowledge of the user until a condition arises where due to the air pockets the radiators fail to function properly.
  
  Then the system is tapped by hand to release the air, as referred to above.
  
  It is well known that water expands when heated. The result is that when the burner is started after the system has been filled with water and the air expelled, the radiators work efiiciently. During the off-cycles the water cools and manual vents that are. not 100 percent sealed take in air.
  
  When the burner goes on and heats the water the water expands again as stated and often the vents cannot release the air quickly enough to avoid forming air pockets, thus cutting down the water circulation in the radiators and lowering their heating efllciency.
  
  For example, during an on and off cycle there may be a decrease in efficiency of, let us say, 5 percent. During each successive cycle this deficiency builds up, due to increased amounts of air in the radiators. It is a known fact that air pockets are detrimental to the efficiency of hot water heating systems because circulation and radiation capacities are lowered thereby. It is also common experience that one or more radiators in every installation having manual vents must be relieved of accumulated air frequently, sometimes several times per week.
  
  I have devised a means, which I will describe fully hereinafter, by which but water heating systems are automatically vented so that air does not interfere with the circulation and so that perfect circulation is maintained at all times.

Other angled automatic air separators or air vents: Aercal from Caleffi

Continuing:

If you can fit an automatic vent into the space that might make your life easier.

Shown below, are two angled air vents produced by Caleffi Hyrdonic Solutions, an Italian company, and marketed unde the AERCAL brand.

Above is the Aercal 504 air separator is an automatic air vent used in radiators.

Below is the Aercal 507 automatic air vent, also produced by Caleffi and used in the end plug on radiators instead of in a separate tapping on the radiator body.

This vent is sold in four models.

• Caleffi S.p.A., S.R. 229 N. 25, 28010 Fontaneto dAgogna (NO) Italy, Tel: +39-0322-8491 Email: info@caleffi.com

You will find Caleffi and other air bleeders and vents

at AIR BLEED VALVE SOURCES

On 2018-01-05 by Dave P.

I just noted that there is also a label stamped on the end of this valve. Taco Vent Patent ( I believe the number is R 601,216)

On 2018-01-05 by Dave P

I am resending another photo of the valve in question. As you can see from the photo, there is no mechanism on the endcap to manually use a square key to bleed the valve.

The only way to turn anything on the existing valve is to turn the set screw on the side of the valve, but the screw head is worn and can no longer be turned with a screwdriver.

I was able to turn the screw on one of my 6 valves, and when I do, it emits water Any other ideas? Thanks!

On 2018-01-05 by (mod) - manually-operated Taco coin vent air bleeder valve

Dave,

Now that I can see your air bleeder control we can be more accurate.

The type of air bleeder valve in your photo is opened manually.

Looking at your photo now provided I think this may be a Taco coin vent.

This is an air bleeder valve that sports a small screw that is opened by a coin or screwdriver to permit air to escape the valve.

Other such valves have a square stem in the valve top that is turned to open it, using, usually, a square key. We discuss opening valves of that type

at AIR BLEEDER VALVES

On 2018-01-05 by Dave P.

Here is a photo of the valve that I referred to. How do I bleed it or does it bleed automatically?

On 2018-01-04 by Dave P.

Thanks for the reply.

I belive that your response refers to a product that is sold by Lowes Home Improvement Store and referred to as a Durst Air Eliminator

Item # 91982 Model # A973, https://www.lowes.com/pd/Durst-Air-Eliminator/3457234.

The air vent valve that I have a question about is a different type, but when I attempt to attach a photo that I took to send to you, the Comment section on your site does not give me the option to Paste a copy of the photo.

Is there a way that I can send you a copy of the photo as a JPG file?

On 2018-01-04 by (mod) -

That air valve should vent air automatically as long as it's screw cap cover has been left loose.

Check the valve by removing the screw cap and pressing in the ce nter valve stem pin. If water squirts out there is no air needing venting at that location.

On 2018-01-03 by Dave P.

I have an air bleed valve on my hot water baseboard heater that is similar to the one pictured on the https://inspectapedia.com/heat/Air_Bleed_Valve_Repair.php page of your website under the section "How to Fix or Replace Corroded or Leaky Manual Air Bleeder Valves".

I am trying to open this valve to remove air from this section of baseboard, but I am not sure how to operate the valve. It is attached to a 90 degree threaded elbow. My valve also has a small setscrew on it, but the head is stripped, so I am guessing that the setscrew must be loosened to open the valve

. If that is in fact how it operates, what can I do to open the valve? If the setscrew needs replaced, do you have any idea what size I would need to replace it so that I can make a quick fix when I am able to remove it.

Otherwise, I will have water leaking while I go to buy one. Or, would you recommend installing a different type of valve at the end of the heating season.

On 2018-01-04 by (mod) - bleeder valve is venting fluid

Mike if water comes out at an air bleeder valve when you open it then there is no air at that location to be vented.

There are two casesd

1. If the air eliminator is an automatic air bleeder valve then it should not be leaking water. If it is, replace the valve.
2. If the air vent is a manual air bleeder and water comes out when you open it, close the valve and try other vents in other locations where piping or radiators are cool or cold.
   
   

On 2017-11-09 by Mike

The first bleeder valve off the circulation pump is venting fluid, and the system pressure is at 0. The boiler still seems to be heating up the baseboard pipes OK though.

Do you think cleaning or replacing the bleeder valve will fix our problem? Seems like the pressure reading might indicate a different or larger problem?

On 2017-10-27 by Frank

Just had a hydronic kick heater installed. There is a manual bleeder valve at the 2nd to last elbow on incoming copper pipe. With system up and to pressure, the hot water is not reaching this heater. All pipes cold. all other radiators are working properly..

When bleeder valve is opened, hot water immediately begins flowing, pipes immediately become hot and fan kicks on. Also, when manually bleeding the water coming out is dribbling-not really under pressure. And the air sounds don't really seem to stop. Then as soon as bleeder valve is closed, incoming pipe no longer receives hot water. Any idea what's happening here?

On 2017-01-02 by (mod) -

Amar:

The repair depends on where the leak is occurring. If the leak is at the base of the air bleeder that screws into the heating unit, then the vent needs to be removed, its threads prepped again with teflon tape or pipe dope, then re-installed. That risks a bigger water leak - such a repair is done with the heating system cool and pressure off or at least reduced.

if the leak is at the vent opening at the top of the device, then the device is defective and needs to be replaced. A temporary - emergency repair: just screw the valve cap shut.

On 2017-01-02 by Amar

Hi there,
My mechanic installed a new air bleed maid o mist 1/8 on the water heating unit on the 2nd floor room. Now it is continuously dripping. What can I do to stop the water from dripping out of it?

On 2015-10-26 by Anonymous

pete again. 2 of 5 radiators on 2nd floor are working

On 2015-10-26 by pete

no heat to 3 radiators on 2nd flr. 3rd floor radiators turned off. open bleeders nothing happens. this is a very old system.

On 2015-03-15 by (mod) -

No.

The part may look identical but the pressure rating of its spring (for an auto tire) is set for much higher pressures. An automatic air bleed valve won't continue to bleed air automagically if you replace the valve stem with one of the wrong rating.

Stop by your plumbing supplier and ask for a new stem or just replace the whole bleeder.

On 2015-03-15 by Linda

Can I use a tire stem valve in the air bleeder?

...

Continue reading at AIR BLEED VALVE SOURCES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

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