Air bleeder valves & automatic air purging valve troubleshooting & repair for hot water heating systems:

FAQs: here we focus on how to find, install, diagnose & fix these devices.

This article series explains in complete detail just how to diagnose and repair problems with air bleed valves and we describe methods used to remove un-wanted, air from noisy or air-bound hot water heating system pipes, radiators, convectors, and baseboards.

Hot Water Heating System Air Bleeder & Vent Troubleshooting FAQs

These questions & answers about heating system air bleeder valve installation, troubleshooting & repair were posted originally

at AIR BLEEDER VALVES - be sure to see the repair advice given there.

Also see this AIRBOUND HEAT REPAIR FAQs INDEX - to all questions & answers about fixing airbound hot water heating systems including air bleeder valves, air vents, and air removal methods.

Article Index

• AIR BLEEDER COMPARED to RADIATOR ON-OFF VALVE
• AIR BLEEDER NOT WORKING - OPENED. NOTHING HAPPENS FAQs
• AIR BLEEDER NOT WORKING - NO WATER COMES OUT, ONLY AIR, FAQs - I open the vent and it keeps hissing, no water ever comes out

...

What's the difference between an air bleeder valve and a radiator on-off valve?

Tip: See details also at AIR BLEEDER VALVE LOCATION - where are these devices installed? Where to find the

Reader question: how do I differentiate between the valve to bleed the baseboard radiator of air, and the on/off valve? I just bought my house and I notice that there are 3 baseboard radiators in one section of the house that are cold. I think that perhaps they are turned off, but I don't know how to tell.

Looking at the radiators, they have pull chains coming out of the top louver, but there's no tension on the chain like there is when you use a pull chain to turn on and off a light, so maybe the pull chains are for opening and closing the louvers?

When I take off the lower cover, the part that covers the fins, I see a valve on the pipe where the water comes in (or out?) that has a slot for a flat-head screw. Would I use that to turn on or off the radiator, or is that the bleed valve? I think it must be the former because I don't see where air or water would escape.

My heat is provided by a gas boiler forcing hot water to baseboard radiators, and I have only one thermostat. And another pertinent detail: In the basement the pipes going to those 3 radiators feel hot, so water is circulating.

In trouble shooting, I want to try the easiest thing first: are the radiators on? Then I'll move on to the more complicated procedures if that's not the problem. But how do I tell if they are on?
Thanks! - Anastasia

Reply: How to tell an air bleed valve from a radiator control valve ?

Above we show a manual hot water heating radiator air bleeder valve that has a round black handle. Because of the handle shape some folks may be confused about just whether this valve is an air bleeder control or a radiator on-off valve.

But it's easy to see the difference. The valve shown at left is attached directly to the hot water heating radiator at its top at one end. It is not connected to hot water piping, so it cannot be controlling the flow of hot water into or out of the radiator.

Now for more details:

At below left we show a common radiator control valve found at the top of a hot water radiator. Other radiator control (on-off) valves may be located close to the floor at the bottom of both steam and hot water radiators.

Below our sketch (courtesy Carson Dunlop Associates ) illustrates an air bleed found at the top of some older radiators - a model that has a tiny round handle. The advice in the sketch to leave air bleed valves alone is for home inspectors.

The worry is that opening an air bleed valve could lead to a leak if the valve is damaged or defective. But in fact manual air bleed valves on heating radiators are a control intended for use by a homeowner, need to be functional to get an airbound radiator back into operation, and need to be fixed if they're defective.

The reason a home inspector might not operate the valve is that during a home inspection s/he doesn't want to risk starting a leak that can't be promptly shut off.

Other air bleeder valves have a t-handle or a square fitting operated with a "skate key" wrench and still other air bleeders use a flat bladed screwdriver for their operation - illustrated in the

article AIR BLEEDER VALVES. In the sketch at above right you can see the radiator on-off control valve at the lower right.

Notice that the radiator control valve will always be connected to both the radiator and a hot water (or steam) pipe, while an air bleeder valve will be connected directly to the radiator.

Well almost. Our photo below is tricky because that particular model of radiator control valve also happens to include a little bleeder fitting - that hexagonal brass nut shown at the center of the radiator control valve body.

 

What's the difference between air vents and vacuum vents on heating systems?

Is there a difference between an air relief valve and a vacuum relief valve? (Dec 4, 2011) DanH

Reply:

Indeed because people discussing plumbing parts may not always be precise nor use exactly the "official" name for a part, the two valve names you cite might be used by some to refer to the same device. But to me, if we are discussing well and water supply systems, then these are different devices.

An air relief valve would allow excess air out of a pressurized system.
A vacuum relief valve would relieve vacuum - the opposite of air pressure.

Can you tell me what kind of equipment on which the valves you name are used? If so I can write a more accurate reply.

 

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Air Bleeder Not Working: Air and Hissing but Water Never Comes Out, FAQs

Tip: See details at

• AIR BLEEDERS NOT WORKING - NO WATER COMES OUT - we open the vent and nothing happens

Radiators always hiss air and water never comes out but the radiators get hot

Our "new" house has two radiators that always hiss air when bled and water never trickles out.

They do get hot, but I'm wondering why I'm always getting air without water. The culprit radiators are on the second floor. On 2016-11-07 by steven

by (mod) - If you cannot ever get water at the air bleeder

Steven

Presuming we're talking about hot water heat - if you cannot ever get water at the air bleeder I suspect these radiators are on an upper floor and that the heating system pressure may be a bit too low to get the hot water up there. CHeck with your heating servicve company.

See PRESSURE & TEMPERATURE SETTINGS, CONTROLS

where you'll find an article section titled "Where do I Set the Heating Boiler Operating Pressure?"

Watch out: if your system is a steam heat system you should not be trying to bleed "air" out of the radiators.

See STEAM HEAT RADIATOR REPAIR and

see RADIATOR STEAM VENTS - home

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...

Opened Air Bleeder Valve - Nothing Happens FAQs

Tip: See more diagnosis and repair at AIR BLEEDERS NOT WORKING - NOTHING COMES OUT - we open the vent and nothing happens

What if nothing comes out of the air bleeder valve when it is opened?

Reader Question: Hi - I have baseboard water heat. Nothing comes out of the air bleeder valves (All but one is manual, they fit a flat head screwdriver.) I just ran water through the whole system to get rid of all the air bubbles.

The pressure on the little gauge looks good and pretty consistent. Now the pipes seem to be hot, but still when I open the bleeder valves I get no water and no hiss of air. Is this normal? Is it ok? Do I need to do something? Thanks very much for your informative articles. - Abby 10/7/12

Reply: here are the most common reasons that opening an air bleeder valve does nothing

If no water comes out of the air bleeder valves I suspect one of these conditions:

1. Temperature & Pressure inadequate: the heating boiler and hot water throughout the system have not been run up to normal full operating pressure: somewhere between 20 and just under 30 psi in pressure and somewhere around 180°F to just under 200°F for a residential heating boiler system.
2. Circulator pump or zone valve problem: circulator is not running or a zone valve (if present) is not open
3. Closed heating line valve or a closed radiator valve where you're trying to bleed air
4. Bleeder Clog: The air bleeder valve body is clogged or blocked.

 

Opened bleeder valve, Nothing came out: no air, no water!

I turned the little skate key device I have to Open the air bleed valve and there was no hiss air or water coming out it mentions that the valve body is clogged or blocked is there any way to easily fix this problem or is it a complicated fix? thx (Nov 19, 2014) marc

Reply:

Marc

The heating system needs to be on and up to operating temperature - check that and try again.

Details of what to do for this situation are

at AIR BLEEDER VALVES

Anonymous said:

11/27/2014 Anonymous

Couple of things-[about what to do if no air comes out of an air bleeder valve] -If your system is not filled with water, you can't bleed the air out of the topmost radiators.

You may need to open the fill valve in the basement, then bleed until air comes out.

Typically, the pressure limiter valve in the basement will drip a little bit after the system is full of water, but usually this stops after a day or so.

Also--if your system has the "scoop" type of automatic air purger, it can still get air bound in the top story of the house. Then you simply have to open the valves in the system in the basement until all the air is out. Takes a while to figure this out.

Reply:

Anon

Good point and thanks for the comment - indeed in More Reading links at the end of this article you'll find two articles

AIR BOUND HEAT SYSTEM REPAIR by PUMP

AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE

that describe how to get past an air-bound system when the bleeder valve alone won't do the trick.

This article series provides a detailed guide to using air bleed valves to get rid of unwanted air in hot water heating systems: fix cold or noisy hot water heating radiators or baseboards. Hydronic heating air vents and air purge devices: types, where to buy; How to diagnose and fix heating system noises & air in hot water heating system pipes.

Service Procedures to force air out of an air-bound hot water heating system.

How to bleed a hydronic (hot water) heating system: how to purge air out of heating system boilers, radiators, baseboards, or piping. What is a baseboard tee, how do they work with baseboard air bleeder valves, how to install air bleeders, vents, purgers.

...

Attic air bleeder vent not working on hot water heating system

We have hot water boiler system and there is air in the lines. The bleeder vent is in the attic and I am not sure how to bleed it. I has a stem that comes out of the top of the bleeder. (Feb 15, 2014) Anonymous

Reply:

Anon,

The air bleeder in the attic should be removing air automatically; If it is corroded or leaky it needs replacement; If it looks clean, try pressing gently on the center pin or valve stem (you may have to unscrew a cap that looks like an automotive tire air valve cap).

Just press the exposed pin briefly with a pen tip or similar instrument. If AIR comes out then the bleeder was not working automatically.

If water comes out STOP PRESSING as you're making a mess and no air is coming out at this location anyway.

If you mess with the valve stem pin as I described and now the darn thing won't stop leaking, just screw the valve cap back on as a temporary fix until the valve can be replaced.

If no air, just water comes out of this valve but your system is air bound, there may be other air bleed valves, automatic or manual, that need to be checked, tested, or replaced; on occasion we have to add a bleeder at a problem spot, and in the worst case we use other methods (described in this article series) to force air out of the system.

Watch out: My consultant Paul Galow suggested I add this warning: in the event of having created a catastrophic leak you'll end up having to turn off heat and turn off water supply to the boiler - an event that seems to me unlikely as long as you keep that valve stem cap to close off the valve if it's leaking or dripping.

But DO NOT use great force turning anything - some of these air bleeder valves are made of thin-walled copper. You can break one right off if you're heavy handed.

 

Drumbeat noises from the hot water radiators

After what sounded like Congo drum playing occurring in my hot water radiators, I tried to investigate.

ll but one radiator was heating up. I have been bleeding the radiators - hear the hissing air until it finally stops, but no water coming out. I've bled them years past where water would escape.

Not sure what is going on. The one radiator that wouldn't heat up now is. Do I need to keep bleeding the radiators until water comes out? Thanks. (Oct 28, 2014) Anonymous

Reply:

See BANGING HEATING PIPES RADIATORS - for diagnosis and repair of this problem

 

Heating system shuts off with a loud bang and rattle

Our system shuts off with a log bang and rattle. Right at shut off is the only time we get air to purge from the pipes but it seems the more we do it the louder it is getting to where I worry we will have a joint blow apart (Nov 19, 2014) Shelley

Reply:

Shelly

Watch out: I'm not sure from just your note what is going on - but it COULD be a *dangerous* puffback or fuel problem. I'd ask for an inspection and service by a trained heating service tech.

See OIL BURNER SOOT & PUFFBACKS

 

Reasons to add air bleeder valves at the end of zones

I've got a 3-zone baseboard heating system that keeps getting airbound.

There's an automatic bleeder by the boiler, but no sign of any bleeders anywhere else.

I'd like to add bleeders at the topmost point of each zone, but the pipe comes up from the floor into an elbow, then immediately into the radiator, then there's another elbow and the pipe goes back through the floor. It seems to me that there's no slack to be able to unsolder the elbow in order to replace it with a baseboard tee.

What are your thoughts on adding the automatic bleeders to each zone in the basement, where I have free access to the pipes? Also, what are your thoughts on using a saddle tee to add a bleeder?

(The circulator pumps are on the far end of each zone, if it makes a difference.) (Dec 3, 2014) LarryM

Reply:

Larry

Sometimes the problem is that we didn't successfully purge all of the air out of the system in the first place. Sometimes it's hard to get all the air out of long horizontal piping runs.

A second possibility is that there is a leak somewhere.

Sure you can add air bleeders at the ends of high end of each zone.

 

After plumbers rerouted heating lines I can't get air out of the pipes and they gurgle

(Feb 17, 2015) SteveF
A few years ago we had a section of our hot water heat removed because we were planning to remove a wall between the kitchen and living room. To make up for the lost heating or those radiators, they put PEX under the floor in the entry way and kitchen only.

But ever since then I can't bleed the system out like I used to. It actually sucks air into the bleeders.

So I've left it alone but I still hear gurgling in the pipes and radiators although it seems to heat fine. But I know it's not as efficient and probably not good for the system. Why would it suck air in? I can take water on my fingers and turn the bleeder and see it get sucked in. Thanks a bunch.

Reply:

Steve,

From your description it sounds as if those air sucking bleeders are not in the right location -leave them closed. Try bleeding from higher bleeders,

Or install a higher located bleeder, or use one of the other methods we discuss for forcing the air out of an AIRBOUND system using a pony pump.

 

Trouble getting air out of my two heat pump zones even using city water pressure

I have been trying to purge my 2 heat pump zone system with little luck getting all the air out. I have put city water pressure into the boiler @ the boiler drain,

forcing the water through each zone pump individually and together with the loop closed and the bleed drain open, all with the gas valve off. ran until no air bubbles were present.

Then I started the boiler up (turned on the gas valve and called for heat) There is still a lot of air in the system.

Can a boiler make its own air when cold water is introduced to the hot system by the fill valve when bleeding? (Mar 3, 2015) David

Reply:

David

There could be a water leak out and air leak into the system, or it could be that you need to use a more powerful air purge approach to force air out of horizontal piping runs.

See

AIR-BOUND HEATING SYSTEMS - home

At the ARTICLE INDEX at the end of this article

David said:
Thanks for responding Dan. I've checked for leaks and I never hear the fill valve open. I've used city water pressure at the drain valve as i've said, and there is little or no air. I've checked the city water for air(none). It seems to me there is only 2 possibilities:

The fill valve is sucking air when I'm bleeding, or as you stated, I'm just not getting enough pressure to force the air out. I also tried using a "L" shaped 1/8" fitting @ the highest point of the upstairs zone with a hose attached and opening an 1/8" valve there and open it when the air comes by. This seems to work as a lot of air comes out.

But it seems to make the air worse, hence my ? about cold water causing air to be released when bleeding. If I shut the gas valve off and try the above method, air comes out for a while then stops. Turn the gas back on, then more air appears.

How can I check my fill valve for "air sucking" and how can I do a more powerful air purge?

Reply:

When the heating system is cooling you can feel with a wet finger whether or not there is suction at the air vent opening.

 

Air Bleed Valve Installation: How & Where to Install Manual Air Bleeder Valves on Hot Water Heating Systems

This topic has moved to a separate article: AIR BLEED VALVE INSTALLATION

Watch out:  if the air vent or air bleeder valve is not installed properly, in the proper position (upright or horizontal depending on valve type and model), and in a functional location (where air can enter the valve or vent) it will not work reliably, may not work at all, and worse, may actually allow air into the water piping system, making the system air-bound frequency worse rather than better. Details are in the air bleed valve installation article cited just above.

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

This topic has moved to a separate article: AIR BLEED VALVE LEAK REPAIR

Air Bleed & Air Purge Valves for Hydronic Heating - Where to Buy Them

Where can I buy canister type air bleeder or air purge valves?

We are unable to find the air bleed valves that you have listed on your web page (canister type). We are looking to buy 10 of them and am wondering if you have a contract from which to purchase these? W.M. - Wacol, Australia

Reply: W.M. please

see AIR BLEED VALVE SOURCES where we list air purgers, air bleeders, manufacturers and sources. For a description of the different types of air bleeders or air eliminating valves you can also

see AIR BLEEDER TYPES & LOCATIONS

...

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

Or see AIR BLEEDER VALVE DIAGNOSTIC FAQs-2 - more-recently-posted questions and answers about using air bleeder valves to fix cold radiators or baseboards

Or see these articles on

Airbound Heating System Repair

• AIR-BOUND HEATING SYSTEMS - home
• AIR BLEEDER VALVES
• AIR BLEEDER VALVE FUNCTIONS
• AIR BLEED VALVE INSTALLATION
• AIR BLEED VALVE LEAK REPAIR
• AIR BLEED VALVE SOURCES
• AIR ELIMINATOR / FLOAT VENT REPLACEMENT
• AIRBOUND RADIANT HEAT
• AIRBOUND HEAT SYSTEM REPAIR by PUMP
• AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE

• AIR SCOOPS PURGERS SEPARATORS
• RADIATOR PLUG REMOVAL

Suggested citation for this web page

AIR BLEEDER VALVE DIAGNOSTIC FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING BOILERS

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