How to Find Out the Age of a Hot Water Heater, Heating Furnace, or Boiler InspectAPedia® -
Here is a Water Heater Data Decoding Document that Aids in Determining Water Heater Age
Here is a Heating Furnace or Boiler Data Decoding Document that Aids in Determining Water Heater Age
How long should a hot water maker or hot water heater last
What factors determine the life of a water heater - independent of the water heater's age?
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Here we explain how to determine the age of a water heater, we provide a chart that decodes the year of manufacture of water heaters, and we discuss the conditions, maintenance, and factors that affect how long a water heater can be expected to last. A chart that decodes water heater age from water heater label data has been provided by NACHI member Scott LeMarr. Also see AGE of Plumbing Materials & Fixtures.
Our photo at page top shows an oil fired water heater with a backpressure problem and other safety concerns like a missing extension tube on that relief valve, and maybe a missing draft regulator and perhaps an oil line that is not protected from damage. The data tags (containing the water heater's age) for this heater are hidden by its insulating blanket. Readers who need to determine the age of air conditioning and heat pump equipment should see A/C DATA TAGS.
How can we determine the age of a residential water heater? By looking at and decoding data on the water heater's label.
Nearly all modern water heaters, electric, oil fired, or gas fired, include data tags and stickers that indicate the year and month of manufacture of the water heater.
That doesn't tell you exactly when a water heater was installed in a particular building but it does indicate the age of the water heater itself.
However some manufacturers encode the year and month of manufacture of their water heater in the product's serial number so that the water heater age is not immediately obvious.
Our photo (left) shows a gas-fired Rheem™ water heater. The label containing the unit's serial number is probably at the water heater top left. The label above the gas control at the water heater bottom typically contains water heater lighting instructions.
Carson Dunlop provide a most-comprehensive Technical Rererence Guide to heating and cooling equipment manufacturers that includes water heater manufacturers. For an encyclopedic reference including manufacturers, history, contact information, and serial number decoding we recommend this book.
Scott LeMarr has generously shared his free Water Heater Age Determination Chart that decodes both furnace age and water heater age. He includes data for many brands of water heater, including hot water systems produced by the manufacturers listed just below.
Water heater age is encoded in data on the information label on these water heaters:
Ambassador water heaters, American water heaters, ACE water heaters, A.O.Smith water heaters, Apollo, Aqua Temp, Aqua Therm, Best water heaters, Bosch water heaters, Bradford White, Cafos, Champion, Crosley, Energy Saver, Envirotemp water heaters, GE water heaters, Glascote water heaters, Golden Knight water heaters, GSW, Hotpoint water heaters, JC Penny, Jetglas, JW or John Wood, Kenmore water heaters (Sears Brand), Lochinvar, Lowes, Mainstream, Maytag water heaters, Montgomery Wards, Knight, PermGlas, Reliance water heaters, Revere, Rheem water heaters, Rheem/Rudd/Richmond water heaters, Rinnai, Security, Shamrock water heaters, Standard water heaters, State/Reliance/Sears brand water heaters, Thermo-King, Vanguard water heaters, US Craftsmaster, US Water Heaters, and Whirlpool water heaters.
Here is A Chart that Decodes the Date of Manufacture of a Hot Water Heater
Our photo (above-left) is from the A.O. Smith EnergySaver water heater in our laboratory. The unit's serial number, MM02-2147713-260 identifies the model and its date of manufacture. The "02" following MM indicates that this unit (in our laboratory) was manufactured in 2002 and the -2 following the MM02- decodes to February.
In a second example, Rheem water heaters provide first the month MM and then the year in the first four digits of the water heater's serial number.
The label shown here includes 0884 at the beginning of the serial number - August 1984.
Mr. LeMarr points out that in the U.S. the remaining actual manufacturers of domestic hot water heater heaters are American, A.O. Smith, Bradford White, and Rheem companies, though their products may be branded among the many names listed just above. LeMarr also informs us that water heaters made in Japan and China are entering the U.S. market. Whenever we have updates to this water heater age and identification chart we'll post the latest version of it here.
How Long will My Water Heater Last? What Determines Water Heater Life?
Home inspectors typically expect a generic water heater to last about ten years. However all of us have found 20 year old models still going strong, while on occasion a newer model fails early.
The chronological age of a water heater (how long ago was it made) is hardly the only factor that determines how long the water heater will last. Here are some other factors that affect the life of a water heater:
Corrosivity of the water supply - more corrosive water may shorten the water heater life or the life of its anode. We discuss various tests of drinking water, including water corrosivity, at WATER TESTS, CONTAMINANTS, TREATMENT. In short, the chemistry of the water being heated affects the water heater life, and aggressive or corrosive water means shorter life for the water heater.
Mineral content in the water supply - if your water supply is high in minerals you may need a water softener - see WATER SOFTENERS for details.
Water heater location - if the water heater is located where it is subject to flooding (as in our photo at above-left) the system is going to be damaged, short-lived, and possibly unsafe as well. Notice the multiple flood-lines on the water tank next to our client? Check out the shoes too. Don't wear white sneakers to inspect a crawl space.
Our next photo (left) shows how a tall water heater was shoe-horned into a low crawl space by digging out a pit to allow the tank to stand upright. This heater is also likely to be exposed to flooding.
We have also seen water heaters placed horizontally to fit into a tight crawl space - a possibly dangerous installation. Unless the manufacturer has specifically designed a water heater to mount horizontally there is risk that the tank or other components will not be properly supported and the system will be damaged and unsafe.
In sum, improper location or improper position of a water heater, such as mounting some water heaters horizontally or locating a water heater in a flood prone location or where it can't be properly serviced or vented can lead to early failure of the heater as well as voiding the manufacturer's warranty.
Water heater installation - improper installation of the water heater, or improper fuel or water piping connections or inadequate chimney venting on fossil-fuel fired water heaters can lead to safety problems or leaks and early heater failure.
Water heater maintenance - flushing mineral debris and dirt from a water heater can significantly extend its life as well as increase the quantity and temperature of domestic hot water the heater provides. If your water heater is making noises (see Water Heater Noises) you probably need to de-scale the heater bottom. See Water Heater Scale - De-Liming Procedures which are discussed at Water Heater Noises.
Water heater anode replacement - the sacrificial anode protects a water heater tank from corrosion. Depending on the chemistry of your water supply, the anode may need to be replaced every few years or even more frequently. If suddenly your hot water (but not your cold water) smells like rotten eggs, the problem may be with a corroded sacrificial anode. See SEWER GAS ODORS and see Check the Sacrificial Anode & Dip Tube of Your Water Heater Tank
Water heater tank type - most water heaters use a glass or porcelain liner which, along with the sacrificial anode, help protect the tank from corrosion. The construction of the water tank, methods and materials used affect the life of the tank, burner, and controls. Look at the water heater warranty period; a longer warranty probably means a more durable water heater tank.
Quantity of hot water used - using more hot water increases the duty cycle of the water heater and exposes the tank to extra risk of corrosion. The temperature to which the water heater is required to heat the hot water may also be a factor in tank or burner or other water heater part life. The quantity of hot water used, which determines how hard it works, is called the duty cycle or level of usage of the water heater (more use = shorter life).
Water heater warranty periods - the warranty for a given model water heater is also a predictor of how long the manufacturer expects the tank to last. (A grouchy friend opined to the author that all of the tanks are the same, but the water heater price is higher on a water tank with a longer warranty period. We have not found data to support this view.) We discuss water heater warranties in more detail just below.
What are the Typical Terms of Water Heater Warranties
Type of water heater tank and water heater warranty - modern "glass lined" water tanks are coated to resist corrosion. The manufacturer's warranty is a clue to how long the company expects their water heater tank to last.
Typical water heater warranty periods for a water heater installed for use by a single family are 6-years, 9-years, or 12-years. But beware: if the water heater tank leaks and fails before the end of the warranty period, if the system has not been properly installed or maintained the warranty may be void. Water heater warranties typically indicate that the tank is warranted against leaks due to rust, corrosion, or chemical action of the water but the warranty will exclude a tank failure due to scale.
The warranty period of a water heater may be encoded in its model or serial number. For example Lochnivar water heaters include a model number prefix that determines whether the heater is warranted for six years or for ten years. If the water heater is in any other use than one-family residential, the heater is warranted for one-year on parts and three years on the tank itself.
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Scott C. LeMarr has provided his file of keys to decode Furnace and Water Heater Age from the data provided on the manufacturer's equipment labels. Mr. LeMarr is
a professional home inspector, Certified Professional Inspector/President,
MASTER Indoor Environmental Specialist (MIES).
Vice President of Wisconsin NACHI. He and his company, Honest Home Inspections, LLC. can be reached at
262-424-5587 or by email to scott@honesthomeinspections.com
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 ($69.00 U.S.). Technical Reference Guide, Carson Dunlop Weldon & Associates, Ltd., 120 Carlton St. Suite 407, Toronto, Ontario, M5A 4K2 Canada, ISBN 1-895585-90-2 165pp.
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In a second example, Rheem water heaters provide first the month MM and then the year in the first four digits of the water heater's serial number. 
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