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Hot Water Heat Air Bleeder Valves: a Guide to Air Bleeders for Radiators, Baseboards, Convectors
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• 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

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 hog when they should includes these key sections:

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. Air purges for steam heating systems are discussed separately at Steam Vents.
2. 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
3. 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.
4. 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 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. 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.

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 the automatic air bleeder valves:

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).
• 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.

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HEATING SYSTEMS
AIRBOUND HEAT SYSTEM REPAIRS
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
BOILERS, HEATING
  BOILER OPERATION DETAILS
  BOILER CONTROLS & SWITCHES
  Air Bleeder Valves

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 Aquastatus for control of hot water heating boilers and tankless coils
• Cad Cell Relays 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 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

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

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
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More Information on Building Diagnostic Inspections and Repairs

• Carbon Dioxide Gas Toxicity
• Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
• Dust from HVAC? An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
• 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
• Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
• National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
• 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
• "Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
• Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
• Installation Guide for Residential Hydronic Heating Systems
• Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
• The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)

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