How Water Heater Works
Hot Water Heaters Explained
How Old Is Your Water Heater? Read More >> Water Heater Decoder Chart Here!
Basically a water heater is a drum filled with water and a heating element to heat the cool water. All water comes into the house or building via pipes. Majority of the year that water is cool. For warm water to be generated for a shower or bath, a dishwasher, or washing machine you will need a water heater. Most homes have the basic water heater but another option would be a tankless version that can warm water on-demand.
While the water heater seems like a simple appliance the inside design is ingenious.
The thermostat is typically set between 120 and 180 degrees Fahrenheit. Usually it is located under a cover plate and has a dial for temperature settings. The dip tube fills the water heater via the home’s water lines and starts the process near the bottom of the heater. The heating mechanism stays on until the water reaches the desired temperature. As the water fills the tank it is heated with the hottest water traveling to the top. The heat-out pipe is located near the top allowing the water heater to utilize the natural tendency of hot water rising. That is how you are able to enjoy your shower and clean clothes and dishes.
Though water heaters are relatively inexpensive compared to the price of a house, repairs for the damage caused when one suddenly has a catastrophic failure is likely to be expensive. This is the reason many inspectors want to at least be able to give their client some idea of how old the device is and when it would be a good idea to start considering replacement.
So, what exactly is the absolute maximum service life to expect? It varies from place to place and is affected by the quality of the product, minerals/chemicals in water, the amount of maintenance the water heater receives and usage. In other words, there is no set in concrete maximum expected service life. In fact, two neighbors with exactly the same brand of water heater installed on exactly the same day on the same street in identical houses can have completely different experiences. In some parts of the country it is normal to expect between 10 and 15 years, while in others a homeowner is lucky if the water heater lasts 10 years.
The manufacturing date is coded into the serial number of water heaters and, since there are more than 100 different brands of water heaer in this country, the thought of trying to memorize every single serial number code at first seems impossible. Impossible that is, until one realizes that only six manufacturers produce those 100+ brands and some share the same basic method for coding, making the task of memorizing the coding methods far less formidable. In this article I'll explain the coding method used by each of the six major manufacturers. At the end of the article, there's a link to a handy decoding chart in TIJ's downloads library.
American Water Heater Company, manufacturer of 52 separate brands of water heaters, uses a 10-digit serial number with a year/week code in the first four digits of the serial number. The year of is the first two digits followed by the two digit week of the year. For example,the serial number 0602****** indicates that the water heater was manufactured the second week of 2006. A complete list of brands manufactured by American is contained in the decoder chart linked to this article.
Prior to 2008, A.O. Smith Corporation, manufactured three brands of water heaters - A.O. Smith, Glascote and Perma-Glas - and used a 10-digit serial number with a letter-month/year code in the second third and fourth digits of the serial number. With this system, the letters A to M, excluding the letter I, are used to designate the months 1 to 12 followed by the two digit week. For example,*H06****** would indicate that the water heater was manufactured in February 2006. In 2008, A.O. Smith acquired State Industries and since then has used the State Industries sequencing (see below).
Bradford-White manufactures two brands of water heater - Bradford-White and Jetglas - and uses a 9-digit letter/number code with two letters signifying the year and month of manufacturer. The letters I, O, Q, R, U, and V are skipped to produce 20-year cycles. These cycles began in 1964 with the letter A, therefore the letter A in the first position of a B-W serial number can represent the years 1964, 1984 or 2004. B-W's second letter corresponds to the month of the year as with the A.O. Smith example above.
Prior to 1973, the month letter was placed at the end of the 9-digit serial number but from 1973 on it has been in the second position. For example, the serial number B********D indicates the water heater was manufactured in April of 1965 but the serial number BD******* can indicate that it was manufactured in April of 1985 or 2005. The trick is being able to distinguish the age of water heaters with the same date codes manufactured after 1973. Fortunately, most home inspectors can do this easily simply by checking the large yellow energy usage tag on the unit to see which ANSI date is posted there. There is one exception to B-W's serial number code that was caused by a computer glitch when some units were manufactured with a serial number beginning with OA - O being one of the numbers that is not used. Any found with a serial number beginning with OA will have been manufactured in January of 1997.
Lochinvar Corporation only manufactures four brands of water heater - Lochinvar, Energy Saver, Golden Knight and Knight - and uses the identical dating code system used by Bradford-White Corporation.
Rheem Corporation manufactures 20 different brands of water heater and uses two different serial number series - one that is all numbers and the other which is both letters and numbers. However, the date code is based on the first 4 digits of the serial number, which signify the month followed by the year, the letter, which is in the 5th position, doesn't need to be considered. For example, any Rheem manufactured product bearing the serial number 0794****** or 0794F***** will have been manufactured in July of 1994.
State Industries was acquired by A.O. Smith in 2008. Prior to becoming part of A.O. Smith, State manufactured 23 separate brands of water heater, including the Kenmore(Sears) brand, and used a letter-month/year serial number code similar to the A.O.Smith model with the letter signifying the month, followed by a number for the year. The difference is that with these the code is in the first three positions of the serial number, not the second, third and fourth as A.O. Smith does it, therefore a serial number C05******* indicates that the water heater was manufactured in March of 2005. After the 2008 acquisition, State began coding the date into the first four digits of the serial number - the two digit year followed by the two digit week; therefore 0912 is the 12th week of 2009.
There are other brands of water heaters being sold in this country that are not made by one of these 6 manufacturers. However, these 100+ brands are supposed to comprise the overwhelming majority of residential water heaters sold in this country today. Once one understands how these serial numbers work and learns to recognize each of the six manufacturer's individual patterns, it's much easier to feel confident that he or she is providing the customer the correct information about the age of the appliance.
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