How to Find Hidden Leaks in or on Hot Water Hydronic Heating Boilers
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Boiler leak diagnosis and repair procedure for finding hidden leaks
How to find out if a hot water heating system is leaking
How to locate hidden leaks in hot water heating systems
How to find leaks in radiant floor or ceiling heating systems
How to diagnose, inspect, evaluate, repair heating boiler leaks
How to inspect & repair central hot water heating boilers - hydronic heating
Baseboard, radiator, convector heat inspection, defects, repairs
Questions & answers about leaks on hot water heating systems: how to find and fix leaks and hidden leaks in boilers, piping, tanks, condensate lines, controls, radiant tubing

Hot water heating system leak diagnosis & repair; here we explain how to determine that a hot water heating system is in fact leaking, and sceond we describe how to find the location of hidden leaks in or on heating boilers, hot water heat piping, baseboards, radiators, convectors, or radiant heat floors or ceilings.

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Tips for Finding Leaks on Hot Water Boilers or in Hot Water Heating Distribution Piping

Readers should also see BOILER LEAKS CORROSION STAINS where we provide a catalog of places where leaks often occur on hot water heating systems. This website answers most questions about central hot water heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect residential heating systems to inform home owners, buyers, and home inspectors of common heating system defects.

The photograph at page top shows that a heating convector recessed into the wall had been leaking into the wall structure for a long time. The leak was discovered by removing the convector cover for direct inspection. We could also see evidence of this leak by inspecting for water stains or damage at the building sills in the basement below.

At above/left our photo shows a severe leak at an air bleed fitting on a hot water heating baseboard line that was eventually separated by freezing and frost-push. While freezing can burst piping and cause serious leaks in buildings, a bad solder joint may be dripping into a wall, ceiling or floor for quite some time before it is detected. Although the leakage rate in a hot water heating piing system increases when the system is hot and in use (and at higher operating pressure than when cold), much of the water leaking out of the piping evaporates.on the hot piping surface.

It is important to recognize and accurately report the significance of rust like this on any heating boiler. We continue to add to and update this text as new details are provided. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Most modern heating boilers include an automatic water makeup valve that combines pressure reduction (to 12 psi cold on the boiler side of the valve) with automatically makeup water if the boiler pressure drops below that point. Details are at Water Feeder Valves, Hydronic Boiler.

How Do I Know if my Heating Boiler is Leaking?

A small water leak in a hot water heating system (hydronic heat) will eventually cause pressure loss in the system, but you may never notice this problem. Leaks on hot water heating systems are likely to occur, or to leak more rapidly when the heating system is hot (at higher pressure) than when it's cool.

The pressure drop from a small heating system water leak may be occurring over a long time, months or longer, and because the leaked-water may simply dry out on the hot heating piping where it is occurring you may never see a wet spot on a floor, wall, or ceiling below the leak.

Our photo (left) shows the mineral build-up at a leaky air purge vent on a hot water heating system. Notice also those white leak stains on the boiler top itself.

How Do I Find Leaks on Hot Water Heating Systems?

To detect a small leak in a hydronic heating system we have had some success with these measures:

Inspect the entire hot water heating system, all hot water piping, the boiler, controls, valves, circulator pumps, piping elbows and piping, baseboards, radiators, air bleeders, etc. for evidence of mineral build-up that indicates a leak. If you have not already done so, take a look at BOILER LEAKS CORROSION STAINS where we provide a catalog of places where leaks often occur on hot water heating systems.
Temporarily turn off the water supply into the heating boiler and monitor the cold pressure of the system when it has shut down. If you see that the cold pressure, shown on your boiler's gauge is slowly dropping, especially if it falls by several psi over weeks or longer (for example over summer months when the boiler is shut down) there is probably a small leak somewhere.

Remember that leaks are faster when the boiler is hot, but reading the "hot" pressure on the boiler won't help in this instance.
For radiant floor or ceiling heating systems that use hot water tubing, borrow or rent an infra red scanner or thermography camera to look for hot abnormal hot areas that spread out around a hidden leak - for example in a concrete floor slab. You'll find that you can easily spot the routing of the hot water tubing; look for an area where the heat spreads out more widely than at other tubing lengths. See RADIANT HEAT.

Look particularly closely where there are probably tubing connectors such as at manifolds and at the start and ends of tubing runs.

Look on floors and other building surfaces, not just at the piping itself. Our photo (left) shows the results of a dripping boiler drain.

A large water leak in a hot water heating system will usually show up quickly as a puddle, a ceiling, wall, or floor stain, or worse, as mineral clogging and damage to the boiler itself, caused by the excessive level of minerals in the constantly-added make-up water (if your area's water supply is high in mineral content).

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Questions & answers about leaks on hot water heating systems: how to find and fix leaks and hidden leaks in boilers, piping, tanks, condensate lines, controls, radiant tubing.

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BOILER LEAKS CORROSION STAINS
BOILER LEAKS, HOW TO LOCATE

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.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book 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. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

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
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.)
Links to our list of additional information on heating system inspection, repair, maintenance
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Tips for Finding Leaks on Hot Water Boilers or in Hot Water Heating Distribution Piping

How Do I Know if my Heating Boiler is Leaking?

How Do I Find Leaks on Hot Water Heating Systems?

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

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