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 Guide to Fixing an Air-Bound Hot Water Heating System - Procedure#2, Using a Portable Pump
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Air Bound Hot Water Heating System Repairs: Here we explain how to remove un-wanted, air from noisy or air-bound hot water heating system pipes, radiators, convectors, and baseboards using a portable pump and drain valves on the heating boiler. We describe 5 methods for getting air out of an airbound heating system and here we detail exactly how to hook up a transfer pump to force water through and air out of an airbound or air-logged hot water heating system. This procedure is also used to add antifreeze to hot water heating boilers.
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Service Procedures to Fix an Air-Bound Hot Water Heating System
 Here we describe the procedure that a heating service technician may use 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.
You can skip this introduction and go right to Airbound Heating System Relief Procedure #2 Using a Pony Pump in the article below if you prefer.
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. Air purges for steam heating systems are discussed separately at STEAM VENTS.
- 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.
- 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
- 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, we explain how to figure out the answer at HEATING SYSTEM TYPES. If your heating system is not working properly, see NO HEAT - BOILER or
NO HEAT - FURNACE. This article series answers nearly all questions about Heating System Boiler Controls on central heating systems to aid in 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 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 here.
If your heating system does include both automatic and manual air-bleeder valves it is possible that you can correct a noisy or airbound heating system yourself. See Air Bleeder Valves and then How to Open Manual Air Bleeder Valves.
Airbound Heating System Relief Procedure #2 Using a Pony Pump
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The following procedure is most useful when a heating system is already hot (we don't want to introduce cold water that might damage a hot boiler), or when a hydronic (hot water) heating system has been filled with antifreeze (we don't want to spill and waste the antifreeze filler).
Most newer heating systems using forced hot water include a service drain at the hot water riser pipe leaving the boiler or if the system is divided into multiple zones using individual zone valves, each heating zone should have a service drain installed, usually near the zone valve.
This procedure for repairing an air-bound hot water heating system is similar to method #1 above except that we connect our boiler drain to a 5-gallon bucket, and we use a pony pump with a short garden hose in the bucket to pump heating water from the boiler bottom service drain into a service drain on the hot water riser pipe or heating zone water pipe.
Forcing water in this manner uses a pump that can produce higher pressures than a heating system circulator pump - it pushes air through and out of the airbound heating system.
Note: this same procedure is used to add anti-freeze to hot water heating boilers & systems for freeze protection. Details are at ANTIFREEZE for BOILERS. |
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Step 1: Turn off the heating boiler, using the service switch. If necessary, see ELECTRICAL POWER SWITCH FOR HEAT.
Step 2: Confirm that the heating system appears to be air-bound: heat is on and boiler temperature is up and the circulator pump is running; by touch the technician confirms that one or more sections of radiator, convector, or heating baseboard remain cold even though all radiator or convector or other circulating system valves are in the open position.
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Step 3: Connect hose from pony pump output side to boiler hot water riser service drain:
Our photo (left) shows a hose connected to the hot water riser pipe at the top of a heating boiler.
Connect the other end of this hose to the output side of a pony pump.
The pump will push high pressure water from the boiler bottom drain into the heating system distribution piping through this heat riser service drain, forcing water and air through the heat distribution piping and radiators and back down through the boiler and out at the boiler bottom.
(Some airbound heating system service procedures may reverse the direction of these flows.)
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Step 4: connect a short hose from the pony pump input side to a 5-gallon bucket.
This photo (Left) shows the black hose connecting the boiler hot water riser pipe to the pony pump output side.
The pony pump's green hose will be connected to the pump's input side and the other end of the green hose will be placed into the blue bucket.
If you are using this procedure not for air removal but to install antifreeze, the bucket connected to the pump's input side contains the antifreeze product. (ANTIFREEZE for BOILERS) |
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Step 5: connect one end of a short garden hose length to the boiler drain valve.
Place the other end of this hose into the same 5-gallon bucket. The black hose (inside the blue bucket in our photo above ) will be connected to the boiler drain (photo at left).
Step 6: open the boiler drain - you should see boiler water flowing into the bucket, covering the ends of both the input hose (from the boiler drain) and the output hose (connected to the pony pump input side).
Step 7: open the service drain on the boiler heat riser pipe.
Step 8: turn on the pony pump. Be sure to keep the ends of hoses in the bucket always covered with heating system water (or antifreeze mix)
Step 9: watch for air bubbles appearing in the bucket. After you see air appearing as bubbles in the bucket, watch for the air to stop.
Also, if you are adding antifreeze to the heating system, this is the point at which you'd use the hygrometer to test the level of freeze protection in the mixture obtained so far.
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Step 10: turn off the pony pump when no more air appears in the bucket,
Step 11: close the service drains on the heat riser pipe and at the boiler drain at the bottom of the boiler.
Step 12: Set the proper boiler cold water pressure: The automatic water feeder will put additional water into the boiler until it reaches its starting pressure.
If the boiler pressure is below its normal level the automatic water feeder should correct this problem.
Watch the boiler pressure fill up to its normal cold pressure setting - typically this is around 12 psi on a two story home.
If the boiler pressure is too high and the boiler is cold, use the boiler drain to drop the boiler pressure to the proper starting level.
See Water Feeder Valves, Hydronic Boiler for a description of the typical pressures needed in residential hot water heating systems depending on the height of the highest radiator or baseboard above the heating boiler.
Step 13: turn on the heating boiler and assure that the thermostat is calling for heat. When the system has reached normal operating temperature and pressure, check the radiators, convectors, or baseboard sections that were previously cold - they should now be warm.
If the previously cold radiator (etc) still remains cold, either you have not removed enough air from the system or there is another problem causing loss of heat. In that case see HEATING LOSS DIAGNOSIS-BOILERS.
Step 14: Check the boiler drain valve and the boiler heat riser service valve to be sure nothing is leaking. In an emergency we screw a garden hose cap on the end of a leaky heating boiler drain or service drain valve.
Step 15: Monitor heating system operation: we never leave a property where we have worked on the heating system without first checking for leaks, inspecting for obvious safety hazards (such as a bad relief valve, blocked flue, improper oil or gas burner operation), and confirming that the heating system runs through it's on-off cycle normally.
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.
What size (horsepower) of Pony Pump do We Need to Force Air out of an Air Bound Heating System?
You should not need a very powerful pump to force water through an air-bound hydronic heating system, since the fact that nearly all of the heating pipes are already full of water means the pump does not have to have enormous lift capacity.
 The Little Giant™ MPFVK115 Portable 115 Volt Non-Submersible Steel Transfer Pump is one that we have used successfully in this application.
This is a non-submersible transfer pump made of stainless steel, operating on 115 Volts, and rated for 365 gallons per hour, produced by manufacturer Little Giant. Part No. MPFVK115. You can purchase that pump from plumbing suppliers or online at Amazon.com.
Thanks to reader David Gould for discussing pump requirements (2010);
Contact us if you have other suggestions for improving this procedure. We are pleased to give credit and links to contributing reviewers, authors, or critics.
Frequently Asked Questions (FAQs) about how to use a transfer pump to force air out of an air-bound hot water heating system.
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Questions & answers on how to get rid of air in an air-bound heating systems by using a pony pump and the boiler supply and drain piping
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Thanks to reader David Gould, BC, Canada, for pony pump requirements discussion, 1/27/2010
- 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.)
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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- Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
- Links to our list of additional information on heating system inspection, repair, maintenance
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