State Water Heater Age
State water heaters come from the A. O. Smith family and use its date code. On current tanks the first four digits are the year and the week. Type your serial below to decode it.
Part of the water heater age lookup
Serial number age lookup
Where to find the serial number on a State water heater
State labels are usually white with the State logo at the top, stuck to the tank jacket. On gas tanks the label is above the gas valve and burner door; on electric tanks it’s between the element covers. You want the line marked Serial Number. The model number above it (for example one starting with GS6 or ES6) describes fuel, capacity and warranty, not the date.
State is common in new construction and in plumber-installed replacements, so if you bought your house with the heater already in place, there’s a good chance the installer chose State or another A. O. Smith brand.
How the State date code works
Because State is an A. O. Smith company, recent State tanks use exactly the same code:
- Tanks built since about 2008: the first two digits are the year and the next two are the week.
1712A045678was built in week 12 of 2017, which is March. - Older tanks: look at the second character. If it’s a letter from A to M, it’s the month (A for January to M for December, no I) and the two digits after it are the year.
KC04123456was built in March 2004.
- Year
- Week
- Not part of the date
- Month
- Year
- Not part of the date
Worked examples
| Serial | Built | Format |
|---|---|---|
| 1712A045678 | March 2017 (week 12) | Year (2 digits) + week (2 digits) (2008–present) |
| 0951B012345 | December 2009 (week 51) | Year (2 digits) + week (2 digits) (2008–present) |
| 2203M123456 | January 2022 (week 3) | Year (2 digits) + week (2 digits) (2008–present) |
| KC04123456 | March 2004 | Month letter + year (2 digits) in characters 2–4 (before 2008) |
Example serials are made up to show the format; they don't belong to real units.
State tanks from before the A. O. Smith era
State Industries was independent until 2001, and tanks from the 1990s and earlier may use a numbering scheme the decoder doesn’t recognize. If yours is that old, it’s well past normal tank life anyway. The manufacture date matters less than replacing it, and you can usually confirm it by calling State support with the serial.
How long do State water heaters last?
The same as any steel tank: about 8 to 12 years in normal conditions. State sells tanks with different warranty terms, from 6-year builder models to longer-warranty ProLine models. The longer-warranty units generally get more anode protection, which slows internal corrosion, especially in hard or aggressive water.
State-specific things to check
- The gas control. If the pilot won’t stay lit on an older State gas tank, the thermocouple or flame sensor is the usual suspect. It’s a cheap fix on a tank that isn’t near the end.
- The flammable vapor sensor. Newer State gas tanks have a sealed combustion chamber with a sensor that shuts the burner down if it detects flammable vapors or overheats. Once tripped, some designs need a part replaced or a technician to reset them. A shutdown doesn’t automatically mean the tank is worn out.
- Leaks. As always, water from the jacket seam or under the tank means the tank itself has failed.
What to do with your result
Under 6 years: check the warranty. The tank may still be covered, and parts often are. Repair rather than replace.
6 to 10 years: service it. Flush the sediment, test the relief valve and consider an anode swap. Start budgeting for a replacement.
Over 10 years: get quotes now. If you’re replacing, it’s worth checking whether a heat pump water heater fits your space, since federal and utility incentives often apply.
A. O. Smith publishes the same coding for its own brand, so the A. O. Smith decoder page is a useful second reference if your serial looks unusual.
Frequently asked questions
How do I find the age of a State water heater?
Read the first four digits of the serial number. On tanks built since 2008 the first two are the year and the next two are the week, so 1712A… is week 12 of 2017, which is March. Older State tanks use a month letter in the second position followed by the year.
Who makes State water heaters?
State Water Heaters started as State Industries in Ashland City, Tennessee, and has been part of A. O. Smith since 2001. Its tanks share A. O. Smith's engineering and serial coding.
Is a State ProLine the same as an A. O. Smith?
They are built by the same company on similar platforms but sold through different channels and with different model names and warranties. For dating purposes they read the same way.
How long does a State water heater last?
Around 8 to 12 years for a typical gas or electric tank. The longer-warranty ProLine models often include extra anode protection, which helps in harder water.
Sources and accuracy
The A. O. Smith / State / Reliance decoder is built from these references and cross-checked between them. Facts are restated in our own words; any mistakes are ours.
Status: being verified against real data plates. Rules last reviewed 2026-10-18; page updated 2026-10-21. Not affiliated with A. O. Smith / State / Reliance. Report a wrong result.
Part of the water heater age lookup
This page covers one brand. For all water heater brands, go to the water heater age lookup.