Hot Water Heat Air Bleeder Valves: a Guide to Air Bleeders for Radiators, Baseboards, Convectors
InspectAPedia® -
Guide to Air Bleeder Valves on Heating Systems: Heating System Radiator, Baseboard, or Convector Air Bleeder Valve Troubleshooting & Repair Guide
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 inspect & repair forced hot water heating systems
Our site offers impartial, unbiased advice without conflicts of interest.
We will block advertisements which we discover or readers inform us are associated with bad business practices,
false-advertising, or junk science. Our contact info is at
InspectAPedia.com/Contact.htm.
Here we discuss 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. 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:
Our discussion of radiators or baseboards that do not get hot when they should includes these key sections:
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.
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.
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, see our introduction at BOILERS, HEATING. If your heating system is not working properly, see NO HEAT - BOILER / FURNACE DIAGNOSIS.This website 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 (this document) 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).
Manual air bleeder valves (photo above) can be opened slightly
and carefully, to permit air to escape. Some heating convectors may have a tapping closed by a plug (photo at left) where an air bleeder valve can be installed - much more convenient than having to remove and replace the plug itself to get air out of the heating system piping.
As soon as water starts coming out of an air bleeder valve it can be closed.
The most common location for manual air bleeder valves on hot water heating systems are on heating radiators and convector units (every one), and at the ends of heating baseboard sections where there has been a previous problem with becoming air bound.
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 the automatic air bleeder valves:
Is there a little cap on top of the air bleeder? many air bleeders use an internal float and an air valve stem that is about the same as the valve stem of an automobile tire valve or bicycle tire valve. The cap over these valves looks just like the cap on the valve stem on a tire (it is).
But on an air bleeder the valve cap is normally left loose so that when the valve has accumulated enough air to move the internal float the valve can open to expel the air.
If the valve cover is screwed down tightly, or if the valve cover has become clogged with mineral debris left by leaking water, air cannot be released. Loosen the valve cap.
If air escapes when you loosen the valve cap on the air bleed valve, that's good.
If the valve cap on your air bleeder is badly corroded (photo above left) the valve probably needs to be replaced.
If water starts to leak out of the air bleeder valve continuously (photo at left) (it's ok for a drop or so to be expelled if the leak stops quickly) then screw the cap down tight again and ask your heating service technician to replace the valve.
If loosening the valve cap does not make water leak out, leave the cap loose.
Is the air bleeder valve corroded? If the air bleeder is thick with corrosion or mineral deposits (photo at left) it has probably been leaking water when it should not, and it probably needs replacement.
If the air bleeder valve is badly corroded or coated with mineral deposits it's safer to leave the valve alone. Picking at a corroded plumbing or heating component of any sort risks starting a leak that you cannot stop without having to shut the entire system down. Call your heating service technician.
Additional automatic air bleeder valves may be installed at other points on the hot water piping, usually at a higher spot near the boiler and sometimes on upper floors in the building. Look for and check the operation of these air bleeder valves too.
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 next photo (below).
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 1: turn on and turn up the heat. First make sure that your thermostat is calling for heat and that the heating system boiler has been running for ten minutes or so - to insure that the system is warm and up to normal operating pressure.
This step is necessary to ensure that heating system pressure will easily push out air from the air-bound radiator or baseboard, and to subsequently force hot heating water into the previously cold radiator or baseboard, confirming that you have successfully removed air that was preventing heat from rising into that unit.
In our photo, the room temperature (bottom scale) is at about 70 degF and the thermostat is set to 65 deg. F - in this condition the heating system will be off and removing un-wanted air in the system would be more difficult.
Step 2: find the air-bound radiator or baseboard: if you have not already done so, once the heating system is up to operating temperature and pressure, check each radiator, convector, or heating baseboard to see if it has warmed up. If you find one or more that remain cold, and provided that the cold heating radiator's valve is in the "open" position (counterclockwise), proceed to step 3 to see if that unit was air-bound.
Our photo (left) shows a manually-operated air bleeder on a heating baseboard.
In a building whose heat is delivered by hot water radiators or by hot water convector units every one of these may have its own individual manually-operated air bleeder valves installed.
If one radiator or convector is not heating up, find and open the air bleeder valve to let out air. Close the valve immediately when water begins to come out.
We hold a cup under the valve spout during this operation so we don't spill water in the living area. (Photo below.)
Step 3: bleed out excess air: Open the air bleed valve (turn it counter-clockwise) and listen for the hiss of escaping air. If no air comes out of the valve, just water, then the radiator or baseboard served by that valve is not air-bound.
A "roller skate key" like device may be needed to turn the recessed square end of older manual air bleeders on radiators and heating convectors.
But in pinch we've been able to open and close the valve using needle-nose pliers (photo at left) that have a point fine enough to reach into and grasp the square end of the valve control.
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.
Other air bleeder valves are opened using a simple flat-bladed screwdriver.
But if the manual, screwdriver-operated air bleeder valve is badly corroded such as the one shown in our photo of a manual air bleed valve at the bottom of a heating radiator (photo at left) chances are it has been leaking and it be stuck.
This particular valve was one we handled with great care. If it was not easy to open and shut it again with a screwdriver (without much force) we'd have chosen to leave the valve alone until it could be replaced.
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.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
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:
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
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).
Mobile View
InspectAPedia ® Home & Site Map
