Here in six steps we describe how to make a reasonable guess at water heater age if the device data tag is missing, incomplete, or simply doesn't match the by-manufacturer heater ages given in this article series.
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.
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If your water heater brand or trader name doesn't appear in the list at WATER HEATER DECODING by BRAND you can use this general data tag decoding guide. Approaches to finding the age of any water heater / cylinder / geyser are given here in six steps
[Click to enlarge any image]
Look for reasonable apparent year encodings in the equipment serial number in format MM YY
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 water geyser age (cylinder age, water heater age) 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.
General approach to decoding unfamiliar water heater serial numbers to get water heater date of manufacture
Typically the manufacturer used
a two digit month and two digit year,
OR
1 digit month that used alphabetic characters
OR
2 digit week (1-52) and 2 digit year
WITH sometimes a plant ID code in the serial number, typically a letter, separating the numeric or other age and serial number digits.
So if we have no other data, we look for a pattern that can decode to a reasonable year using those schemas.
Using Rheem water heaters as an example many, not all, water heaters made by Rheem were sold under other brand names such as Montgomery Ward.
Modern Rheem water heaters use a 10 digit code:
MMYYX12345 where X is the plant code and 12345 a consecutive unique ID and of course MM YY are month and year.
A Signature 500 electric water heater (or geyser or cylinder depending on where you live) looks like a much newer installation. I see light colored wood 2x studs (recent construction) and shiny copper electrical wiring at the ground connection at the heater top. Also I see the use of modern red PEX tubing used for the temperature/pressure relief valve discharge tube.
Certainly the heater could be older than its present wiring and plumbing, but if those are any guide, this is not a very old unit.
Depending on where you live we could get a more accurate estimation of the year of installation of the water heater plumbing as presently shown even before finding the heater's data tag (which I am betting is there somewhere). PEX surged in popularity in the U.S. beginning around 2000.
For example, in the United States, California, one of the last adopters, did not approve the use of PEX (cross-linked polyethylene tubing) for household plumbing until 2007 (on a case by case basis) and not until 2009 for all homes.
More about PEX plumbing pipes used for building water supply and hot water heating applications can be read
at PEX PIPING INFORMATION.
...
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