A.O. Smith Water Heater Age by Serial Number

For the modern A.O. Smith water heater serial-number format shown here, the first two digits give the year and the next two give the manufacturing week. A number beginning 2038 means week 38 of 2020. The second pair is a week number, not a month.

Below, we decode a real A.O. Smith hot water heater label from WHE’s photo library and explain why older formats and barcode scans need care. For other manufacturers and our label-reading tool, use the main Water Heater Age guide.

How to read the code · Real label example · Older serial numbers · Warranty and installation dates

Find the A.O. Smith Rating Label First

Photograph the exterior rating label so the model number, serial number and manufacturer’s name are readable together. Include the entire serial-number line, even if part of it is separated by a space. A close photo identifies the unit; a second, wider photo helps an installer understand the equipment and its location.

Avoid confusing the model number with the serial number or a separate item/part number. On the label below, all three appear next to one another. Only the serial-number date code is used in this example to determine the age of the hot water heater.

A.O. Smith Water Heater Age by Serial Number: Read YYWW

A.O. Smith’s US Service and Warranty Guide (PDF, page 10) illustrates a serial number beginning 1719: year 2017, manufacturing week 19. The same YYWW order applies to the matching modern label shown here.

Read the complete example as 20 | 38 | 121051908. Do not interpret 38 as a month, and do not assign an exact installation day from this code. If the year/week reading does not make sense for your label, have A.O. Smith confirm it.

Real A.O. Smith Label: Week 38 of 2020

This photo shows model ENT-40 110 and serial number 2038121051908. Its date prefix identifies week 38 of 2020. The model number and the separate item/part number describe the equipment; neither replaces the serial-number date prefix.

Keep the original photo with your home records. It is more useful than a note saying “2020 heater,” because a service provider can also read the complete identification when checking parts or reviewing a replacement.

Why a Barcode Scan May Not Give the Complete Date

A.O. Smith’s serial-number format notice (PDF, page 3) describes an October 2016 change involving a nine-digit serial number with a printed four-digit YYWW prefix. In the format described there, the barcode contains the nine-digit serial number without that date prefix.

Labels and barcodes vary. Photograph and read the printed serial-number line rather than relying only on a scan. In our photo, the number printed below the barcode includes the 2038 prefix. Do not assume every barcode includes it—or that every barcode omits it.

Older A.O. Smith Serial Numbers and Unfamiliar Formats

Older hot water heater labels can look different from this numeric example. Do not automatically convert a letter to a month or apply the first-four-digit rule to an unfamiliar pattern. A.O. Smith’s format notice itself shows a previous serial-number style containing a letter; the presence of a letter is not enough to choose a decoding rule.

If the label is faded or the code does not fit, send A.O. Smith the complete model and serial number, plus the clearest photo you can take. Keep uncertain characters marked as uncertain instead of guessing between a zero and the letter O. A readable original invoice may also help establish the installation history.

Brand rules are not interchangeable. Our Rheem water heater age guide shows why another manufacturer’s week/year arrangement should not be applied to an A.O. Smith hot water heater.

ProLine, Signature and Lowe’s Models

Whether the equipment is a ProLine model from a plumbing professional or a Signature model sold at Lowe’s, its product-family name and retailer do not tell you when that individual unit was made. Read its rating label and confirm any unfamiliar format with the manufacturer.

For local equipment options, visit our A.O. Smith installation and replacement page. Our A.O. Smith warranty guide explains the separate coverage questions for professional and retail hot water heaters.

Manufacturing Age Is Not the Installation or Warranty Date

A manufacturing code tells you when a water heater was made. Keep the installation invoice to document when it was put into service. Record both dates if you know them; do not replace a missing installation date with a guessed one.

To check coverage, use A.O. Smith’s official warranty verification page and the applicable warranty certificate. Have the complete serial number and installation records ready. The date-code calculation alone does not establish remaining coverage or whether labor is included.

A.O. Smith Water Heater Age Questions

Does 2038 mean my A.O. Smith hot water heater was made in 2038?

Not in the modern YYWW format illustrated here. Split it into 20 and 38: the year is 2020 and the manufacturing week is 38.

What if my serial number contains a letter?

Keep the whole code and identify its format before interpreting it. Do not assume a letter always means a month. Ask A.O. Smith to confirm a pattern that differs from the documented examples.

Does an older hot water heater automatically need replacement?

The date is useful for planning, but it does not describe the condition of the tank or components. Review the service history, any current problem and your household’s needs. If an insurer or HOA has set a deadline, keep its written request with your records.

Help With an A.O. Smith Hot Water Heater in Palm Beach County

Water Heating Experts helps local homeowners evaluate equipment and plan service or replacement. Text the label and a full installation photo to 561-602-9062, or call us. Include your city and describe what you need help with.

For replacement planning, explore our sizing guide and water heater selector, then request a free installation estimate. Contact us directly to discuss repairs.