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Here we explain 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. We illustrate how to buy and add air bleeders at baseboard elbows using a baseboard tee and air bleeder valves.

If a hot water heating system develops too much air in the piping you may hear bubbling or gurgling in the heating pipes when the heating system is operating, or worse, so much air may be in the heating piping, radiators, or baseboards that heat may simply not circulate at all.

Here we explain how to locate, inspect, use, or replace automatic and manual air bleed valves on hot water heat, and we explain methods used to remove air from air-bound hot water heating systems by finding and repairing or using automatic or manual air bleeder valves, or by using two different service procedures to force air out of airbound pipes in a hot water heating system. This article is divided into these main sections:

Beginning at AIRBOUND HEAT SYSTEM REPAIRS, our discussion of radiators or baseboards that do not get hot when they should includes these articles on how to get rid of air in hot water or hydronic heating systems in order to prevent or cure air-bound heating systems (sections of baseboard or radiators that don't get hot):

1. Air Bleeder Valves - a Guide to Air Bleeder Valves for Hot Water Heating Systems: Radiators, Baseboards, Convectors - how to find and use manual and automatic air bleeders to fix noisy gurgling heating pipes or an airbound heating system. Our photo left (red arrow) shows a conventional air bleeder valve on a cast iron hot water heating radiator.
   
   The blue arrow shows the little nipple out of which air will hiss when the valve is opened (using a rectangular "skate key" type wrench or key available from your plumbing supplier). Close the valve as soon as water starts squirting out from this opening.
2. Air Scoops, Air Separators, Air Purgers: Since on many hot water heating systems a key air bleeding or air vent point is at the air scoop or air separator closer to the boiler, see Air Scoops Purgers Separators. Air purges for steam heating systems are discussed separately at Steam Vents.
3. Airbound Heating System Relief Procedure #1 Using Water Feeder & Boiler Drain - how to use built-in controls and valves to force air out an air-bound heating system whose radiators, convectors, or baseboards are not warming up
4. Airbound Heating System Relief Procedure #2 Using a Pony Pump - how to use a portable pump, short sections of garden hose, and heating system valves to force air out an air-bound heating system whose radiators, convectors, or baseboards are not warming up.
5. Water Feeder Valves, Hydronic - a defective automatic water feeder valve on a hot water heating boiler can result in too little starting water pressure in the system - radiators on upper floors may fail to receive heat. On a steam heating boiler a defective automatic water feed valve can cause the heating system to shut down completely or can lead to boiler damage or even unsafe conditions. At BOILER PRESSURE & TEMPERATURE SETTINGS we discuss the pressures needed for hydronic or hot water heating systems - a taller building needs higher starting (cold) pressure in the heating boiler. At Water Feeder Valves, Hydronic we discuss problems with water feeder valves that also control water pressure in the boiler and we explain how to adjust the water feeder valve and thus boiler water pressure. If your heating system uses a steam boiler, see Water Feeder Valves, Steam.

Readers should also see Diagnose Oil Heat Noises for diagnosis and repair of other heating system noises on both oil and gas fired heating equipment. This website answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

If you don't know what kind of heat your building uses, we explain how to figure out the answer at HEATING SYSTEM TYPES. If your heating system is not working properly, see NO HEAT - BOILER / FURNACE DIAGNOSIS. This article series answers nearly all questions about Heating System Boiler Controls on central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.

A Guide to Air Bleeder Valves for Hot Water Heating Systems: Radiators, Baseboards, Convectors

Heating Baseboard Air Bleeder Valves what are these valves for, where are they found, how do we use them? Air bleeder valves are installed on hot water heating systems to remove unwanted air from the heating boiler, from hot water heat distribution piping, and from radiators, convectors, or baseboards. Our photo (left) shows a manually operated air bleed valve at one end of a hot water heating baseboard. In this case freezing has caused the pipe connection to pop loose and leak - a different problem.

What Are the Functions of Hot Water Heating System (hydronic heat) Air Bleeder Valves?

Air bleeder valves, both manual and automatic, are used forced hot water heating systems to remove un-wanted air from the heating distribution pipes and radiators.

Carson Dunlop's sketch (left) shows a common location for the air bleed valve on a cast iron radiator. The advice to leave this valve alone is intended for home inspectors who don't want to risk spilling water on someone's floor or opening a valve to find that they can't close it again. But if your hot water radiator or convector is staying cold even though the heating boiler is running and hot, it may be air-bound and you'll need to bleed out the air.

Why is it necessary to get this air out of heating lines?

Air trapped in hot water heating piping, radiators, baseboards, or convectors makes the heating system noisy with gurgling or bubbling sounds if there is just a little air in the heating system.

But if the volume of air becomes too great, the heating system will simply stop delivering heat to the occupied spaces, some or all of them, in the building. Why? A heating circulator pump is capable of pushing water around in the loop of heating baseboard but is often not capable of overcoming a section of baseboard that contains a large bubble of air. It's necessary to remove such air blocks. If air blocking has been recurrent a previous owner may have installed air bleeders at strategic points.

See Air Bleeder Valves for details about how to get an individual cold radiator working again if it's air bound, and see AIRBOUND HEAT SYSTEM REPAIRS if the cold radiator, convector, or baseboard problem seems to affect all of the heating radiation devices on all or part of an individual heating piping loop or zone.

What are the Types of Air Bleeder Valves and Where are they Found on Hot Water Heat Systems?

Automatic air purge devices (photo at page top) are available and are usually installed right at the heating boiler but sometimes additional ones are needed at higher levels in the building.The two most common locations for automatic air bleeder valves on hot water heating systems are on top of the heating boiler itself (photo below right), or on a special air-scoop and air purging device found on the hot water heating piping just over or near the heating boiler (photo below left).

How to Diagnose and Repair Hot Water Heat Air Bleeder Valve Problems

Check hot water baseboards, radiators, or heating convectors: if some of these heating devices are hot and others cold, are they all on the same heating zone? Feel the hot water piping leaving the heating boiler - it should be hot when the boiler is running and the thermostat is calling for heat.

If the building has multiple heating zones each zone will be controlled by its own thermostat and each heating zone will either have its own hot water circulator pump (controlled by a thermostat and pump relay switch), or each hot water heating zone will have its own thermostat and a zone valve that opens to let a common circulator pump send hot water through that individual heating zone. Are all of the thermostats turned up high enough to call for heat in each heating zone?

If some heating baseboards or radiators are hot and others cold and we're sure that they're on the same heating zone, then the system is probably air-blocked.

How to Get Un-wanted Air out of a Hot Water Heating System

Virtually every hot water heating system has one or more air bleed valves installed. On most hot water heating systems there is at least one automatic air bleed valve, usually located on the heating boiler itself, or close to the heating boiler on a nearby check valve or flow controller.

Inspect and fix or replace any leaky float-type automatic air bleeder valves (air vents):

Inspect and use or replace manual air bleeder valves on the heat distribution piping:

• Problem spot manual air bleed valves: If a building heating system has experienced previous problems with air blockage in the heating system a technician may have installed a manual bleed valve at a strategic location to get air out of a problem section of piping. Look for valves that resemble the one shown in our photo.
• Problem spot air bleeder valves on hot water heating piping or baseboards can be hard to find, usually at the higher end of a section of heating baseboard that has become air-bound in the past. An example is show in our "Step2" photo below and at "how do I add a manual air bleeder valve on hot water heating baseboard piping" later in this article.
• Leaky air bleeder valves: I do find leaky air bleeder valves on heating systems in two common circumstances:
  • The manual air bleed valve was left open or was abused by a heavy-handed operator who over-torqued its fittings and damaged screw threads or a seating gasket
  • The air bleeder valve is of the automatic float and canister type rather than manual type; among these. Automatic air bleeders, to work, require that their little screw cap (it looks like and is a tire valve stem cap) be left loose so that the float inside the automatic air purger/bleeder can release air when needed.
    
    But on some of these devices the float eventually sticks or becomes waterlogged and the automatic air bleeder dribbles and leaks, as you can see in our photos above. Usually automatic float type air bleeder valves are installed at the boiler where it's easy to see and replace leaky ones during boiler service. I don't recommend using float type automatic air bleeders at heating baseboards inside the building where they may be hidden by baseboard covers and can leak into and damage the building for some time before anyone notices.
• Also see SOLAR COLLECTOR AIR or GAS COLLECTION for a discussion of automatic air bleed valves on solar collectors.

How to Open Manual Air Bleeder Valves on Heating Radiators and Baseboards to Bleed Out Air - step by step guide

Here we describe the procedure for using manual air bleeder valves to remove un-wanted air in a hot water heating system in order to correct noisy gurgling pipes or to correct loss of heat due to an air-bound radiator, heating convector, or section of hot water heating baseboard.

If your hot water heating system has become air-bound (one or more sections of heating radiators or baseboards are staying cold even though the boiler is on and the circulator pump is running), and if your system does not have an air bleed valve to remove air blocking water flow, you probably need to call a heating service technician who will use one of the methods we describe at Airbound Heating System Relief Procedure.

Step 4: close the air bleeder valve. When water begins to come out of the valve, close it.

Step 5: feel the heating pipes entering the baseboard, radiator or convector. In a minute or so the pipes and radiator should begin to warm up and eventually become hot. If this does not occur either the heating system is off, there is another airbound location, or there is a separate problem with the heating system. In that case see HEATING LOSS DIAGNOSIS-BOILERS.

How Do we Know That the Air Bleed Valve Operation Has Been Successful?

• If you open a manual air bleeder valve on a hot water heating system and air hisses out, there was air that needed removal. If only water comes out, that device was not the one that is air bound.
• If the heating boiler is already running and hot, quite quickly, in a minute or three, the radiator or convector that was air bound will get hot to the touch. Feel first at the pipes that enter the radiator, convector or heating baseboard since that's where hot water will begin entering the previously air-bound device.

Frequently Asked Questions (FAQs) about Hot Water Heating System Air Bleeders & Vents

Question: 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?

Appreciate any help you can provide.

W.M. - Wacol, Australia

Reply: Identification Photos of Types Hydronic Heating (hot water heat) air vents or air purge valves & where to buy them

We distinguish among several types of heating system air bleeder valves or air vents:

1. Manual Air Bleeder Valves or vents - found on radiators and at high-end elbows on heating baseboard runs, are opened manually to vent air from air bound or noisy heating systems at which you've observed or heard air bubbles moving through the system. (Photo, above left). At least some manual air vents include a tiny "spout" not just a hole through which to bleed air. The spout allows you to catch any water that squirts out of the vent during the bleeding process.
2. Hygroscopic automatic air bleeder valves or vents - look like a manual air bleeder valve but are left open and are designed to vent air automagically from the system. Watch out for leaks and corrosions and replace any of these valves that are leaking. (Sketch, above 2d from left). Automatic radiator vents and hygroscopic air bleeder vents will be provided with air vent holes but no little spout.
3. Automatic, float-type air bleeder valves or air vents - use a larger canister and float design and, provided you leave the valve cap open, are designed to automatically vent air from the system. We install float type air vents at high points at or near the heating boiler. (photo, above, third from left)
4. How Water Heating Radiator vents include manual and automatic air vents for hot water heating systems (image of a modern European automatic radiator vent is at above 3rd from right). Two very common hot water radiator air bleeder valves are shown at above right and 2d from right. See Radiator Control Valves & Vents for details.
5. Steam Vents are not discussed here but are detailed at STEAM HEATING SYSTEMS.

There are several manufacturers in the U.S. and Canada who provide both automatic and manual air vents for hydronic heating system, as we list below. Some of these manufacturers have world-wide operations as we indicate below. You may need to use a different term that is country dependent when searching for these products, such as air eliminator. .

• Bell & Gossett provides air eliminators or air vents under both brands such as B&B Models ATF-20, IAS, ABF, and AFTL that work with hot water heating systems. B&G IAS and ATF-20 are residential air eliminators (air vents), and the AFTL is a commercial air eliminator used in other applications.
• Maid-O'-Mist® Automatic and Manual Air Elimination Valves, also for hydronic, steam, and solar applications, contact:3217 N. Pulaski Rd. | Chicago, IL 60641 , Tel: 773.685.7300 - E-mail: info@maid-o-mist.com, website: http://www.maid-o-mist.com/
  • Automatic air valves
  • Jacobus Steam Vents
  • Float Control Valves
  • Auto Vent 670
  • Auto Vent 675
• Honeywell Corporation (worldwide operations) produces several air vent models Floatvent, Supervent SV473, and Maxivent (Model Maixvent FCV 147 or 147A) - www.honeywell.com
  • Honeywell Sparco products include both residential heating system air eliminators and commercial air eliminators such as their model PV200T and PV800FC.
• Spirotherm, 25 N. Brandon Drive Glendale Heights, IL 60139, produces air eliminators for residential hot water (hydronic) heating systems such as their VJS075 - Website: http://www.spirotherm.com/air/
• Thrush Co., Inc., Thrush Co. Inc. 340 West 8th Street Peru, IN 46970, USA, Tel: 765-472-3351, Email: customerservice@thrushco.com. Thrush Co. produces residential air purge and air elimination devices for residential heating systems such as their Model 706 Automatic air vent and their Model 720 Automatic Air Eliminator, Model 721 automatic air eliminator (handles all sizes of piping) . - website: http://thrushco.thomasnet.com
• Watts® Water Technologies, Water Safety & Flow Control Products, website: http://www.watts.com/
  815 Chestnut Street North Andover, MA 01845 USA, Tel: 978-688-1811, or
  5435 North Service Road Burlington, Ontario, Canada L7L 5H7
  • Watts DuoVent (high capacity) air vent, 1/8" to 1/4" or 3 to 8 mm
  • Watts FV-4 automatic air vent, 1/8" to 1" diameter or 3 to 25 mm
  • Watts HAV automatic vent valves, chrome plated, 1/8" to 1/4" or 3 to 8 m
• Contact your local hot water or steam heating service companies or their suppliers. Both manual and automatic steam or hot water air vent valves and their parts are very common and should be available locally at plumbing and heating suppliers.
• In Australia, try Honeywell Pacific (website http://www51.honeywell.com/pacific/ ) or Hunt Heating, POB 294, Braeside VIC 3195 ABN 50 354 796 935, website: http://www.huntheat.com.au or their showroom in Keysborough VIC 3173 provides the Picobello air vent for radiators and should be able to provide point you to a source of automatic air purge valves as well.

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

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

Anastasia:

At left 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 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.

At below right 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 above on this page. 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 at above left 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.

A tricky way to "shut off" radiators in older homes by not bleeding air out of the radiator

Sometimes in older homes the heating radiator control valves are stuck and cannot be operated. Usually the radiator valve will be stuck in the "open" position because no one wants to live with no heat in cold weather. When we lived in a 100 year old home in Poughkeepsie, New York, ever fall we found that some radiators had become full of air over the summer when the heating system was off.

For a few rooms where we didn't want heat, and where the radiator control valve was "stuck" in the "open" position, we found that if we simply neglected to bleed air from that radiator it wouldn't heat up when the rest of the heating system was operating.

Over at RADIATOR VALVES & HEAT CONTROLS you'll see more photos of radiator control valves. On all hot water radiators the heating control valve that turns the radiator on or off will be at the hot water inlet pipe to the radiator and may be located near the radiator top or bottom. There are a few air bleeder valves that have a tiny round handle, maybe 1" in diameter, but they will be mounted right onto the radiator body itself, not on the piping.

Question: Installing air bleeder valves: how do I add a manual air bleeder valve on hot water heating baseboard piping

Hi Dan, How do I install a manual bleeder valve on my baseboard heating pipe? Can I tap into the 90 degree elbow with a 1/8 drill bit and sweat a bleeder valve? Are there any other alternatives to incorporate a manual bleeder to the baseboards in the house? - Simon.

Reply: Here is how to buy and install a Heating Baseboard Tee - a special 90 degree elbow that has a reinforced 1/8" NPT tapping and solder it in place at system high points

I was disgusted when a Poughkeepsie plumber we recently hired to install heating baseboard tossed aside the air bleeder fittings I had left to indicate where I wanted them installed.

At left are the two baseboard tees I had purchased, along with their air bleeder fittings, ready for installation. The plumber (whom I am leaving nameless) left them on the floor - his real reason: he took a shortcut that saved maybe five minutes on the job by using the pex to copper 90's (with no tapping for an air bleeder valve) that he had on his truck.

When I complained, his retort was that air bleeders are not needed and that they were in his opinion a liability (because he fears they'll leak) rather than an asset.

While it's true that in a perfect world, with a combination of luck, Air Scoops Purgers Separators that magically capture 100% of problem air in the heating system, and perfect plumbing routing you can purge air from at least some hot water heating systems at initial installation. But it's just plain stupid to think that over the life of a hydronic heating system there will never be an air problem in the piping. It's not a perfect world, and "stuff happens", ya know?

So I do not agree with that plumber, nor do heating experts nor the manufacturers who produce a wide variety of valves to manually or automatically purge air from hot water heating systems. As we were installing a new heating loop on an upper floor addition on a one story house, it's likely that air entrained in the heating water or that appears in heating system ever in the future will rush upstairs.

Now I'm going to have to drain down the system and remove his work and install the proper fittings myself.

Stop by your local plumbing supplier. They can sell you a special elbow, a baseboard tee, usually bronze (see our baseboard tee image at left), that solders in place to replace the existing 90 degree elbow at either end of your baseboard run. The baseboard tee looks like a 90 degree elbow but technically it's "Tee" because it has three openings - the two 3/4" copper pipe fittings and a third 1/8" tapping that is installed pointing "up" to accept the bleeder valve. These are inexpensive fittings, typically around $4.00 U.S.

The baseboard tee or elbow includes a raised casting with additional bronze 1/8" NPT tapping already threaded to accept the bleeder fitting itself. Our page top photo shows a similar tee made of cast iron.

Under a heating baseboard cover, at the start or end of the baseboard run, because of space limitations (under the baseboard cover) and for reliability I prefer to use simple manual bleeder valves at baseboards - they're solid and bullet-proof.

Baseboard tees are also available for other types of heating piping systems such as PEX tubing, and in mixed sizes such as 1/2" x 1/8" x 1/2" and 1/2" x 1/8" x 3/4" diameters to fit the PEX, bleeder valve, and 3/4" diameter copper baseboard piping. If you are working with standard copper heat piping you probably need one or more 3/4 " x 1/8" x 3/4" baseboard tees.

When I was actually working for a living and had to try to fix air-bound heating baseboards in some older homes (see Air-bound boilers & radiators) it was standard practice to install at least one of these bleeder fittings at the highest point on any baseboard run that was giving problems.

My photo (left) shows a baseboard tee with an older type of air bleeder valve installed at a home where there had indeed been a baseboard piping leak. But the leak didn't occur at the air bleed valve, which had been safely shut.

The leak happened when the home lost heat and the piping froze and burst. You can see a section of new copper piping that had been soldered in place during repair work on the home.

You'll want to do he job if adding one or more heating baseboard tees and its air bleeder fitting before the heating season begins so that you won't mind shutting down and cooling off the boiler. You'll need to drain the heating line so that you can de-solder the old elbow and then solder the new baseboard tee in place.

I advise AGAINST drilling and tapping in an air bleeder into an existing elbow even though it's technically possible to do so. The worry is that the 90 is just too thin at the point where you'd drill; even soldering an air bleeder in place I would be forced to agree with my irritating plumber, that in that case the fitting would not be reliable. It's not worth a leak and water damage and mold contamination from a leak that will naturally happen while no one is at home.

Incidentally small amounts of air WILL circulate around through the system as bubbles and can get caught and vented by an air bleeder right at the boiler or its riser pipe. That's why you'll usually find an air bleed in that location. (See our page top photo).

Finally, if you take the annoying plumber's view, you can eschew any air bleeders and instead, wait until the system is air bound and you've lost heat.

Then one can, using boiler drain and feed fittings, force higher pressure through the system to try to blow air out of those uppermost heating baseboards. Of course that' a heck of a lot more trouble than just loosening a bleeder valve screw and letting the air hiss out at the high point(s) in the system.

At Air-bound boilers & radiators we discuss alternative methods for removing air from an air-bound system.

Question: Installing air bleeder valves: Advice for installing remote or secondary air bleeder valves

When installing an automatic air bleeder on a system is it possible to install a tee at the high point then run a line to a different location and install the auto air bleeder in the secondary location, and will it work if that secondary location is lower than the tee in the main line? - Steve

Reply: the high point air bleeder valves are most important on hydronic heating systems but air bleeders in other locations work also

Steve you will sometimes see automatic air bleed valves at various heights and locations on heating system piping, and all of them will work to release air that finds its way to each of those locations. However it's most likely most important to include an air bleeder at the highest point in system piping where air may be found.

You can run a tee at a high point, as in your question, and then add a more remote air bleeder, provided that all of the piping slopes horizontally or better, uphill from the tee.

Small amounts of air in a hydronic heating systems are sometimes pushed around by the circulating water and may reach even lower air bleeders. But the circulator can't push large amounts of air - the system can become air bound unless means are provided for getting rid of it.

Question: Installing air bleeder valves: Is it ok to install an air bleeder valve by just drilling and soldering into an existing copper pipe elbow on the heating line?

Hi Dan,
I've hired a HAVC guy to put replacement slant-fin baseboard heaters. because some of the stubs are coming from the wall, he claimed that he can't install a regular bleeder but have to drill a hole on the elbow and solder one in place. Is this the right way to do it? thanks. - Lily

Reply: not recommended

Lily

My OPINION is that drilling and soldering a bleeder valve into an existing copper elbow is an unreliable "fix" to add an air bleeder - the risk is that the soldered fitting is not strong enough and that you have a leak, worst when no one is home - and a flooded building and costly repairs.

If it were my house I'd cut away the wall and solder the necessary fittings in place, or I'd look a second time to see if there is not another location that will do.

Question: Installing air bleeder valves: which end of the heating baseboard gets the air bleed valve

Should the air vents be installed on the inlet or outlet of the baseboard heater? - Ron Thompson

Reply: at the outlet end or at both ends of the baseboard

Ron, if I were installing only one manual air bleed valve I'd certainly place it at the end of the heating baseboard so that I could force air out of that baseboard section.

On difficult or long baseboard runs I like to install bleed valves at both ends of the baseboard run. In that case I might install an automatic air bleed valve at the input end of the baseboard and a manual air bleed valve at the end of that baseboard run. In that manner, as long as the automatic air purge or air bleed valve keeps working air shouldn't enter the baseboard run.

But if air does get into the system, from a bad valve or from a sudden large surge of air, some of which gets past the front end air bleed valve, I can still purge the problem air from the system without having to follow other more complicated, lengthy, and expensive procedures.

Question: Installing hot water heating piping air bleeder valves: leave the bleeder cap loose?

There is a lot of great information here. Definitely helpful for some things and the images are also a plus.

I have one 8' stretch of baseboard pipe that isn't heating up. It's the middle room (my 1 y/o sleeps there) of 3 bedrooms. Both other bedrooms are fine. There are 2 new automatic bleeder valves on each end of the baseboard. I've tried slightly opening the screw valve with no luck. There is a supply and return on this stretch of baseboard (monoflow system?). The lower pipes get hot but it's not making it past the valves to the coils.

I am lead to believe this is the highest point in the house. I've tried turning the system on and than bleeding and still unsuccessful. As mentioned, both bleeder valves are fairly new with no corrosion or water leaks. What else can I do? Dad needs his sleep as his little one keeps waking him up so help is abundantly appreciated. - LB

I have cracked one of the valves and an ever so slight amount of air comes out but not enough to get the water flowing. I'm guessing I may need to bleed all the water from the system and start from scratch. I'm just glad that it appears to be an air blockage and not something more serious.

Just for reference, I should keep the caps slightly open to allow air to dispel when necessary or should I keep them tight and manually crack them from time to time? - LB [continued]

Reply: it depends on the air bleeder valve type

LB:
If a section of baseboard is cold but pipes leading to it are hot quite possibly it is airbound as you suspect. Possibly the air bleeders are defective; with the system at full operating pressure and temperature, careful (avoid burns, spills) manual bleeding might dump enough air to get things going, else you may need to try replacing one or both valves.

Or use the alternative air purge methods at AIRBOUND HEAT SYSTEM REPAIRS (article link at page left)

LB:

If you're not getting the air out at a bleeder and you're sure the bleeder is not clogged, be sure that the heating system is up to operating pressure and temperature. If still you can't get the air out, you'll need to force water through the piping at higher pressure.

Finally, we can categorize air bleed valves on hot water heating systems into roughly two groups:

Automatic air bleeders, often including a float valve that drops to open the bleed valve to purge air when air accumulates in the float body - on these valves the manufacturer instructs to leave the valve cap loose so that the valve can vent automatically. An automatic air bleeder at the boiler or in a utility area should pretty much always have its cap left loose so that it can do its job.

Manual air bleeders, usually don't even have a cap, but might. These are kept closed except when in use.

Watch out: an automatic air bleed valve with a loose cap, installed on a heating baseboard in the living area, can present a risk of water leaks into the building floor (or ceilings below), if it's not inspected and if necessary cleaned or replaced. In this location some heating techs and plumbers avoid the leak risk by just keeping the cap tight on the valve. The valve won't automatically purge air (you are relying on other air purgers elsewhere in the system for automatic air purging), but it can still be opened and activated if necessary to purge air from the particular high hot water piping loop that it serves.

Question: installing heating piping air bleeder valves: do I need air bleed valves at both ends of the piping run?

My home has several zones with base board hot water radiator. the problem zone is divided by a stair case between two rooms. The plumber installed no bleeds. he simply made a 90 degree rise 7 feet to the top of the landing then across 10 feet to 90 degree 7 foot drop to the other room. This makes the 7 foot stair case landing the highest point for this zone. I now have an air lock. Do I put a bleeder valve on both the right and left side of the landing? (PS..I am now very proficient at complex copper sweating.) Is there a rule dictating how short or long a run need to be before needing to add 2 bleeders. melvincoke@yahoo.com

Reply:

Melvin, I don't think you need two bleeders if you can get one at the end of that high point in the piping - by "end point" I mean that for that high horizontal run, put a bleeder at the end of the run (where the pipe heads back down) that is more distant from the boiler feed side. That is, it's on the "return" end of that high leg.

Then with the bleeder in place, when the system is up to operating temperature and pressure, if you open the bleeder, the system pressure should push the air out.

Recapping: I like bleeders at both ends of high runs myself, but in truth you should be ok with just a bleeder at the far end from the feed side of the boiler.

Let us know how it goes - the results will help other readers.

Follow-up comment:

A [lumber friend came by said the same thing you said Dan. However, we both feel sometimes saving $6.00 costs hundreds or thousands. So we ended up just placing bleeders at both ends of the high point. I tested your theory by filling the system and only bleeding system using the valve installed at the return side bleed and the system worked.

So thanks very much for your help.

Reply: plumber shortcuts on heating piping diameter and air bleeder valves cost plenty later

I agree with you completely. The owners and contractor were disgusted when Paul A., somewhat of a bully plumber in Poughkeepsie, saved himself some labor time and "saved" the customer essentially nothing by installing smaller diameter hot water heat supply piping to and from a building addition.

Paul also saved himself labor time by refusing to install two air bleeders on the high loop in the system even though we bought the bleeders and left them on the floor at the locations where they were to be installed. When questioned he explained that "half-inch heating piping is just fine, and you don't want those bleeders anyway - they're a liability - they always leak".

The smaller heat supply piping he used failed to consider the design specifications for the heating system - an assumed hot heating water flow rate through the baseboard, combined with a high-output heating baseboard design had permitted the use of about half the normal linear footage of baseboard in the room. Now if the heat is found to be inadequate the owners will have to either ruin their design by adding baseboard, or they'll have to rip out ceilings to install larger diameter heating water piping.

And about leaving off those air bleeders: sooner or later over the life of the building, when that high heating pipe loop becomes airbound, the occupants will have to hire a heating or plumbing tech to go through a more troublesome (and costly) procedure to fix the airbound heat problem. If Paul had taken the trouble to make a first-class installation, one could have just opened a screw and bled out the air in minutes.

Question: Winterizing the heating system: Is it OK to drain un-used heating zone piping, baseboards and radiators?

I have a boiler with 5 heating zones. I am living alone in a big house and do not use the rooms for 3 of the zones. I would like to know if I can drain those zones so they don't freeze and just use the 2 remaining zones for heat.

Thank you - Anon

Reply:

Sure, provided your heating zones are individual piping loops, and that you have control valves at both ends of the un-used heating zones, you can drain them and leave them turned off.

Watch out to get all of the water out of the piping. It can be difficult to get water out of long horizontal pipe runs without blowing air through the system.

More details about how to winterize the heating system when you are going to leave heat "OFF" are found at Winterize- Heat Off Procedure. Also see how WINTERIZE A BUILDING

Question: Winterizing the heating system: Can I put antifreeze in the heating system instead of draining it?

I've read the other parts of your website as you suggested and I hope you don't mind more questions. Instead of trying to drain the heating zones I don't need, can I just put a non-toxic antifreeze in the whole boiler system? It sounds easier if it is a good solution.
Thanks again!

Reply: use an antifreeze intended for use in heating boilers and piping

Sure, there are specific antifreeze products intended for use in hot water heating systems. Also see WINTERIZE A BUILDING

Question: Heating Zones: How can I determine how many heating zones I have?

I took a look at the boiler. I see the 5 zones going off the outbound pipe, but I only see 2 converging back to the intake. Do you think that means the zones are not all individual loops? - Lisa

Reply:

Most likely you have

5 individual room thermostats
5 individual heating zones
5 loops of hot water heating piping leaving the boiler (one at each zone valve)

but at some convenient locations the installer joined several of those individual zones into one of two return lines - that's why you see just two hydronic heat (hot water) lines returning to the boiler.

You can still drain and turn off 3 of the zones but you'll need a plumber to find the END of each of the loops you want to turn off - right where it joins a common return line. There s/he will install a drain and control valve.

The risks of turning off heat completely, besides my previous warning about not getting all the water out, are that you freeze up plumbing somewhere. If the zones do NOT heat any rooms with plumbing you may be ok.

An alternative, and the one that I use, is to keep all 5 zones working, but set the thermostats for the three unused areas to a lower than usual temperature, just high enough to avoid freeze-ups - say 45 degF. You'll save significantly just by dropping the thermostat set temperature.

In an unfamiliar home I might try dropping the thermostat set temperature gradually in very cold weather, double-checking to see just how cold the room gets. You'll want the zones to run occasionally to protect against freezing.

Finally, for freeze protection advice for the building, see WINTERIZE A BUILDING ( a link I'll add at page left).

Question: Winterizing the heating system:Can I shut off the first radiators in the heating zone without losing heat in the rest of the house?

I have such a system, and only one zone. The thermostat is located in the warmest room in the house. Causing frigidity and numbness of extremities in other areas of the home. Since the location of the thermostat is also where the first radiator is in the home, can I "shut off" that baseboard radiator, and the next one, without losing heat to the rest of the home? - Jacke

Reply: It depends ... on how heating piping is arranged

Jacke

Whether or not you can shut off or turn down the first two radiators or baseboards in your home to improve heat distribution depends on how the piping is arranged.

If all of the baseboards are piped in series (which is usual for single-zone hot water baseboards) then the input of each baseboard is fed directly from the outlet of the one prior. In that case you can't turn off any baseboard because 1. you have no shutoff valve installed and 2. more important, you'd be shutting off all hot water flow through the system.

If you have radiators, heating convectors, or even some baseboard installations that are piped in parallel, that means that there will be a loop of hot water heating piping that runs through the buildings and that off of that loop, individual risers and returns feed individual radiators or convectors (heating baseboard is not usually piped this way).

In this second case it would be possible to turn off an individual radiator or convector.

So part of my long answer is due to confusion on my part - you use the terms radiator, then baseboard radiator - so I'm not sure what you've got.

Let us know the details - what we learn will assist others.

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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• For details about the setting, re-setting, or function of the controls and switches commonly found on hot air heating systems see these articles:
  • Hot Air Heating Furnace Basic Operating Steps
  • Guide to Heating System Components: see BOILER CONTROLS & SWITCHES and FURNACE CONTROLS & SWITCHES and STEAM HEATING SYSTEMS or if appropriate for your building, RADIANT HEAT. If your building uses a heat pump, see AIR CONDITIONING & Heat Pump SYSTEMS
  • Air Bleeder Valves for Hot Water Heating Systems: Radiators, Baseboards, Convectors
  • Aquastats Heating Boiler Primary Controls: A guide to Aquastats for control of hot water heating boilers and tankless coils
  • CAD CELL RELAY SWITCH on oil fired furnaces or boilers as flame sensors & safety devices
  • Check Valves Guide to check valves and backflow preventers on hydronic hot water heating systems gas or oil fired
  • Draft Hoods on gas fired heating equipment, function and safety
  • Draft Regulators & barometric dampers on oil fired heating equipment
  • Expansion Tanks Guide to pressure control and expansion tanks on hydronic hot water heating systems gas or oil fired
  • Fan Limit Switch on hot air furnace heating systems gas or oil fired
  • Flue Gas Spill Switch on gas fired heating equipment sense combustion and protect from blocked flues
  • Gas Piping, Valves, Controls including gas regulator assembly and other controls
  • MIXING / ANTI-SCALD VALVES: Guide to mixing valves on hot water heating systems and radiant heat systems
  • Noises: see Diagnose Oil Heat Noises
  • Power Switches to turn on or off heaters for furnaces & boilers, oil & gas fired, heat pumps or electric furnaces or boilers
  • RELIEF VALVES - TP VALVES: A guide to temperature and pressure relief valves & safety controls on hot water and steam heating systems
  • Stack Relay Switches Explained on oil fired furnaces or boilers as flame sensors & safety devices
  • Steam Vents provides details about air vents or steam vents on steam heating systems and diagnoses hissing sounds and failure of a steam radiator to get hot.
  • Thermostats & Heat Controls for furnaces & boilers, oil & gas fired, heat pumps or electric furnaces or boilers
  • Water Feed Valves: A guide to water-feeding/pressure-reducing valves on hot water and steam heating systems
  • Zone Valves: A guide to zone valves for heating zone control on hot water heating systems
• Carbon Dioxide Gas Toxicity
• Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
• DUST CONTAMINATION FROM HVAC? An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
• Fuel Oil & Oil Heating Magazine, 3621 Hill Rd., Parsippany, NJ 07054, 973-331-9545
• Goodman Furnace High Temperature Plastic Vent HTPV safety recall US CPSC notice
• Home Heating System Should Be Checked [for proper venting and for CO Carbon Monoxide Hazards - DJF]
• Inspection Procedures for Oil-Fired Heating Systems Detailed step by step approaches for inspecting complex systems]
• Lennox Pulse Furnace Safety Inspection/Warranty Program: Carbon Monoxide Warning
• Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
• Oil Tanks Above Ground, UL Standards, guidance for home owners, buyers, and inspectors
• Plastic Heating Vent Pipe & Other Heating Safety Recall Notices
• Weil McLain Model GV Gas Boiler/gas valve CPSC recall/repair
• The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
• Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
• The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
• Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
• "Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• "Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• Installation Guide for Residential Hydronic Heating Systems
• Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
• ...