BOILER LEAKS CORROSION STAINS - CONTENTS: 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
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Heating boiler leak repairs: here we explain how to detect, diagnose, find, & evaluate leaks in or on hydronic heating boilers with focus on residential heating boilers, including leaks leading to loss of heat, heating boiler noises, leaks, odors, or smoke, and high heating costs.
This article series answers most questions about central hot water heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects.
Our photograph at page top shows severe rust at the tankless coil on a steel heating boiler - this boiler may be beyond repair even though the rest of the unit looks pretty good.
When a tankless coil-mounting surface on the boiler itself is severely rusted it may be impossible to get an adequate seal when
bolting on a new hot water coil, making it necessary to replace the entire heating boiler.
See TANKLESS COILS for more about this device.
[Click to enlarge any image]
It is important to recognize and accurately report the significance of rust like this on any heating boiler.
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Even significant boiler water leaks at a tankless coil (left and at page top) may never show up on the building floor as a wet spot, leading an owner to ignore a condition that can lead to very expensive damage. When observing evidence of leaks on a heating boiler, keep these points in mind:
Even serious leaks may never show up as "wet" spots: A boiler may be leaking but you may see no actual water: during the heating season the boiler may always be hot, causing small leaks on the boiler or on heating piping to simply evaporate. But such leaks will usually be visually very evident: look for a build-up of corrosion, green or white or other colored mineral salts, or look for rust or water stains on the equipment.
Surface rust, light, superficial rusting, is generally repairable. Clean the area and fix the leak when the boiler is next serviced and monitor for any future leaks.
Exfoliation, or thick flaking rust on any boiler but particularly on a steel heating boiler is very serious, possibly not repairable, and risks loss of the boiler as well as sudden loss of heat in the building. The boiler shown at left might be repairable. The boiler shown at page top was so badly rusted that simply replacing the coil and its mounting plate might not possible - the boiler might have been ruined by this unattended leak.
Warning about corroded leaky heating system and plumbing parts: Don't Poke at Leaks and Corrosion on heating equipment.
Heating service technicians may be more daring, if they are prepared to immediately replace a ruined boiler or a catastrophic leaking part. We watched a heating company rep poke his pencil right through a badly rusted boiler.
But a home owner or home inspector should look but don't touch corroded leaky parts on a boiler. Too often the mineral build up from corrosion is all that's holding back a serious leak that could, by chipping away the deposited gunk, result in a rapid leak so severe that the heating equipment has to be immediately shut down - not a good idea in freezing weather.
Internal heating boiler leaks: Some critical heating boiler leaks may be internal and not visible by simple inspection, such as a leak inside the boiler heat exchanger (photo at left) which may pass water into the combustion chamber.
A service technician or a skilled home inspector should be able to spot evidence of these leaks by inspecting for subtle clues (rust at the bottom of the boiler jacket) or by removing the boiler external covers (as in our photo).
Leaks related to temperature or pressure: Some leaks occur only at peak operating temperature: e.g. at relief valve.
On some heating boilers such as some cast-iron units, leaks may occur between boiler sections when the system is cold - on these models some technicians prefer to keep a little heat in the boiler year-round to avoid this problem. Leaks between boiler sections may be repairable but if left unattended can destroy the equipment.
Watch out: Leaks anywhere in the hot water heating system can cause more than pressure loss in the heating system. Leaks can also allow air back into the heating system as it cools, leading to excess air, even abnormally high pressure (less common), or noisy heat piping or circulator pumps.
A Catalog of Common Heating System Leak Points - Where to Watch for Heating System Leaks
Note: the following catalog of common places where you may find leaks on a hot water heating system boiler or its components is arranged alphabetically. Some of these leaks, such as at TPR valves, are dangerous and require urgent attention or even system shut-down.
Air bleeder vent valve leaks - leaks can occur at automatic air bleeder valves or air vents wherever these vents are installed on hot water heating systems including at baseboards, expansion tanks, air scoops, or radiators.
See AIR BLEEDER VALVES used to purge air from hot water heating piping, baseboards, radiators, and from the boiler itself.
see AIR SCOOPS SEPARATORS PURGERS - these devices use an automatic air purger or air bleeder valve and may leak at fittings or at the valve itself.
see EXPANSION TANK AIR VALVE LEAKS
Boiler control setting-caused leaks: Leaks due to improperly-set boiler controls - temperature set too high - can show up as leaks at the TPR valve.
see BOILER LIMIT SWITCHES
Bolt opening leaks - suspect hidden damage - can occur at any bolt connection that connects boiler compnents. For example
see TANKLESS COIL / HOT WATER COIL LEAKS for an example of severely rusted coil mounting bolts that are probably beyond repair
Boiler section leaks between cast iron boiler sections of a cast iron boiler, possibly occurring where the push nipples or seals join the water passages of individual cast iron boiler sections together. A photo showing cast iron boiler sections is just above
at HEATING BOILER LEAKS, INTERNAL.
Boiler crack or split leaks in a cast iron boiler section, also leaks at a crack, split, or rust perforation of a steel boiler.
Circulating pump mounting flange leaks -
see CIRCULATOR PUMP LEAKS . Our photo (left) shows a closeup of an active leak at a heating system circulator pump.
Expansion tank / compression tank leaks due to water-logged expansion tanks - occur when the expansion tank has lost its air charge.
See EXPANSION TANKS
and TANKLESS COILS for a guide to diagnosing, evaluating, and repairing leaks at the tankless coil.
Also Pipe fittings at face of coil plate - look for mineral salts and rust stains since small leaks will evaporate without leaving visible water or wet areas
See TANKLESS COIL / HOT WATER COIL LEAKS for photos of this type of leak stain
Temperature / Pressure Relief Valve TPR Valve Leaks: Leaks at the boiler temperature/pressure relief valve. This leak may be very dangerous as corrosion from water passing through the valve may prevent its safe operation in an emergency. The boiler pressure/temperature relief valve may be leaking because the system pressure or temperature is too high - it's working properly; or the relief valve may be leaking because its internal gasket has failed or because it has become jammed partly open by corrosion and mineral debris build-up.
Prompt expert inspection and repair are needed. Watch for leaks below the valve's mouth or discharge pipe (a pipe should extend from the relief valve to a few inches from the floor) or watch for corrosion at the tip of the discharge pipe. Gently feel inside the tip of this pipe to see if it's wet. DO NOT TRY TO TEST or open or operate the relief valve itself.
Watch out: a dripping or frequently spilling T&P valve is dangerous because those very leaks can eventually cause the valve to clog and then to fail to open when it should.
See RELIEF VALVE LEAKS
Watch out: never try to fix a leaky temperature / pressure relief valve by using a boiler leak-stop product - you are risking
Zone valve leaks - occur at the piping connections or at the connection of the zone valve head or motor and controls to the zone valve body.
See ZONE VALVES, HEATING
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will replacing a face plate fix boiler leaks?
(June 4, 2014) Anonymous said:
over time the rust area is expanding. will replacing the face plate solve the problem?
If the rust is superficial, replacing the face plate and face plate gasket as well as careful cleaning and sealing during reassembly should work. If by "expanding" you mean swelling flaking exfoliating rust as we illustrate in this article series, then check the boiler face plate mounting area (on the boiler) with care since failure to seal at that surface means leaks will continue.
Question: presence of white effloresence - calcium - salts - scale as a leak diagnostic
(Aug 26, 2014) greg mcleod said:
Lots of calcium around copper joints . Had a couple leaks over last time6 years plus i drained a few times. Zone valve seem sticky and recently replaced. Seems like air valve plugged. What do you think is wrong
Greg what you describe sounds like high mineral content in water clogging up components. It's a bit odd to find that in a hot water heating system as the same physical water stays in the system indefinitely - so I might also look for a leak or other cause of frequent makeup water being added.
Question: high gauge pressure, TPR valve leaked, mopping up constantly - how do I get the pressure back down?
(Feb 12, 2015) Anonymous said:
i have a boiler system that heats a 1 and 1/2 floor house. the pressure on the gauge is way above the highest reading. Two nights ago the pop off valve released some of the pressure I am assuming because it created a racket in the basement and you could hear the releasing of steam. Mind you I know it leaks. I have a tube running to a drain from the pipe that is suppose to be used for the purpose of the releasing of water pressure (I assume). I use to empty a mop bucket 3 times a day, is how bad this leak is. I have had a tech come to check way it was leaking....all he did was tighten the hose clamp I have on the pipe and hose I have rigged up, so I don't have to empty a bucket. It is now winter and gets below freezing temps and the boiler does not keep up with heating the house. How do I get the pressure to get back into a normal range (20psi)? I am worried that it is going to blow my boiler completely and I will not have any heat.
You are describing an unsafe heating system; I'd shut it off and call for emergency service. It it were just a modest leak I'd not be so worried but when you describe high enough pressure that the TP valve is spilling then the system is at overpressure and unsafe. An exploding boiler is a catastrophe in all senses.
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"The Fight Against Corrosion - A Study of the Nature of Corrosion and its Problems in Water Services and Heating Systems", Daniel Davies, Research and Development Services, Stansted Mountfichet, Essex, England, World Plumbing Conference-IV, "Plumbing and the World Environment, Compendium of Workshop Papers, October 3-6, 1996, Hyatt Regency Chicago, Chicago, IL", [personal correspondence, DJF - Author, July 2011]
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & 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 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.)
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates 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.
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.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones