Water Heater Age Lookup: Decode Your Serial Number
Read the serial number off the rating plate, pick the brand and get the manufacture date and age, with each brand's date rule and its source shown.
Reviewed October 24, 2026 · Free to use · Bookmark it for next time
- 10–15 yrsstorage water heater life (DOE Energy Saver Guide)
- 8–12 yrsaverage tank heater life (A. O. Smith)
- 142 mg/LGrand Rapids plant-tap hardness, 2025: hard on the USGS scale
- 20 yrsBradford White's year-letter cycle
Find Your Water Heater’s Age
Copy the serial number exactly as printed on the rating plate. Spaces and dashes are fine.
Your entries stay in this browser for your next visit.
Where to Find the Rating Plate
The rating plate is the printed label on the heater’s outer jacket, and it carries the model number, the serial number and the brand. A. O. Smith points owners to the nameplate on the side of the unit; Bradford White shows the plate on gas, electric and tankless models.
- Tank heaters: check the side of the jacket for the nameplate (A. O. Smith).
- Tankless heaters: check the outside of the wall-hung cabinet; Bradford White shows the plate on its tankless models too.
- Serial vs. model: the serial follows “Serial,” “Serial No.” or “S/N”; the model number names the product line.
- Printed date: Rheem’s newer labels print the manufacture date on the third line, per its Bulletin 1207.
Keep hands off the burner area and hot pipes on a running gas heater; a phone photo of the plate reads just as well.
Wall-Hung Units
Tankless heaters carry the plate on the cabinet. Rheem’s Bulletin 1207 covers its tank, tankless and heat pump labels with one serial format.
Gas and Electric Tanks
On a tank, the plate sits on the jacket near the controls. Write the serial number and model number on the first page of the owner’s manual for the next service call.
How Each Brand Dates Its Water Heaters
Each manufacturer hides the build date in a different part of the serial number. The table shows the rule the tool applies and where it comes from.
| Brand | Date Rule | Example | Rule Source |
|---|---|---|---|
| A. O. Smith | Digits 1–2 = year; digits 3–4 = production week (up to 53) | 17 19 … = week 19 of 2017 | Manufacturer service guide |
| Rheem, Ruud, Richmond (2012 on) | Plant letter, then week, then year | M 14 12 … = Mexicali, week 14 of 2012 | Manufacturer Bulletin 1207 |
| Rheem, Ruud, Richmond (older) | Digits 1–2 = month; digits 3–4 = year; then a plant line letter | 09 12 D … = September 2012 | Manufacturer Bulletin 1207 |
| Bradford White | Letter 1 = year (20-year cycle); letter 2 = month (A–M, no I) | J M … = December 1992 or 2012 | Manufacturer date code chart |
| State | Newer: year, then week. Older: month letter, then two-digit year | M 07 … = December 2007 | Inspector guides (check the plate) |
| American, U.S. Craftmaster, Whirlpool | Digits 1–2 = year; digits 3–4 = week | 01 28 … = week 28 of 2001 | Inspector guides (check the plate) |
| GE | Ignore leading letters; digits 1–2 = month, 3–4 = year | 11 08 … = November 2008 | Inspector guides (check the plate) |
| Kenmore, Navien, Rinnai | No single published rule | — | Rating plate or maker’s support line |
Bradford White’s two-year letters: the year letter repeats every 20 years. Its production number ran 7 digits before December 2007 and 8 digits after, so a 9-character serial dates before December 2007 and a 10-character serial dates after. When both readings still fit, the tool shows both years.
What Your Water Heater’s Age Means
Age is the first number in any repair-or-replace decision. The U.S. Department of Energy puts storage water heater life at 10–15 years and tankless life at more than 20 years. A. O. Smith gives its tank heaters an 8–12-year average and tankless heaters 15–20 years with proper care.
- 10–15 yrsstorage heaters (DOE)
- 20+ yrstankless heaters (DOE)
- 8–12 yrstank average (A. O. Smith)
- 15–20 yrstankless (A. O. Smith)
A. O. Smith treats a tank heater more than 10 years old that leaks around the base of the tank or operates erratically as due for replacement.
Signs a Water Heater Is Failing
Symptoms point to specific parts, and A. O. Smith ties several of them to the end of a tank’s life.
Water at the Base
A tank over 10 years old that leaks around its base is a replacement case, per A. O. Smith. Water at a drain valve or relief valve pipe points to that part instead.
Popping or Rumbling
Strange noises usually mean sediment at the tank bottom, which a flush clears. Noise that returns after a repair points to a failing element or a cracked tank, per A. O. Smith.
Erratic Hot Water
Erratic operation on a tank older than 10 years falls in A. O. Smith’s replacement group. Discolored or smelly hot water comes from hydrogen gas reacting with harmless bacteria in the tank, per the same source.
Smell gas near a gas water heater? Leave the building, then call 911 and the gas utility from outside. Water spreading toward an outlet or panel: stay out of it and keep the power off at a dry location.
Test the Relief Valve Once a Year
The temperature and pressure (T&P) relief valve on the top or side of the tank opens when the water gets too hot or the pressure too high. Bradford White’s gas water heater manual sets this check at least once a year.
Hot water discharges under pressure. Bradford White warns that lifting the lever releases hot water under pressure; keep people and anything that water damages clear of the discharge pipe. Its manual adds that scalding occurs within 5 seconds at a 140°F setting.
- 1
Check the Discharge Pipe
Confirm the pipe from the valve runs down toward the floor or a drain and that nobody stands in front of its outlet.
- 2
Lift the Lever
Lift the lever at the top of the valve several times, until the valve seats properly without leaking and operates freely (Bradford White).
- 3
Watch It Reseat
The valve passes when it seats without leaking and moves freely. One that keeps dripping or sticks with lime crust needs service. Bradford White: never plug the valve outlet.
A valve that discharges on its own from time to time points to thermal expansion in a closed water system; Bradford White sends owners to the water supplier or local plumbing inspector to correct it. The DOE Energy Saver Guide gives 120°F as a water heater setting safe for most people.
How Grand Rapids Hard Water Ages a Water Heater
Grand Rapids tap water is hard. The city’s 2025 Average Water Analysis lists 142 mg/L of hardness (8.3 grains per gallon) at the plant tap, inside the U.S. Geological Survey’s 121–180 mg/L “hard” band.
The USGS explains the cost: heating hard water leaves calcium carbonate deposits that shorten equipment life, raise heating costs and lower the efficiency of electric water heaters. A. O. Smith calls hard water the biggest threat to tankless heaters, because mineral buildup damages heat exchangers.
Drain a Gallon
Bradford White’s gas heater manual: drain off a gallon of water monthly to remove silt and sediment. The water comes out hot.
Or a Quart
The DOE Energy Saver Guide: drain a quart from the tank every 3 months to remove sediment, following the manufacturer’s directions.
Inspect the Anode
Bradford White sets anode rod inspection every 2 years and more often in homes with a water softener, which speeds anode wear.
Hardness differs by town: Wyoming-supplied suburbs test moderately hard, and some township wells test far harder. The Water Hardness by Town lookup shows the figure for each of 25 Grand Rapids-area towns. For a heater that is leaking, noisy or out of hot water, see water heater repair in Grand Rapids.
Common Questions
Where Is The Serial Number On A Water Heater?
The serial number sits on the rating plate, a printed label on the side of the tank jacket. A. O. Smith directs owners to the nameplate on the side of the unit for the model and serial numbers, and Bradford White shows the plate on gas, electric and tankless models. On a tankless heater, check the front or side of the cabinet.
Is The Manufacture Date The Same As The Installation Date?
No. The serial gives the date the factory built the heater, and installation comes after shipping and sale, so time in service runs shorter than the age the serial shows. A receipt, a permit record or a date the installer wrote on the tank gives the installation date.
Why Does My Bradford White Heater Show Two Possible Years?
Bradford White reuses each year letter every 20 years: its chart lists A as 2004 or 2024 and M as 2015 or 2035. The tool drops any year in the future and uses the production number length (7 digits before December 2007, 8 after) to rule years out. When two years still fit, both show, and the house's history settles it.
How Long Does A Water Heater Last?
Storage water heaters last 10–15 years and tankless heaters can last more than 20, according to the DOE Energy Saver Guide. A. O. Smith gives tank heaters an 8–12-year average and tankless heaters 15–20 years with proper care.
Why Can't The Tool Decode My Kenmore Or Tankless Serial?
Kenmore is a Sears store brand, and the InterNACHI dating chart lists no date rule for it. This tool found no serial date rule published by Navien or Rinnai, and independent guides disagree on their formats. The rating plate, the owner's manual or the maker's support line dates those heaters.
Sources and How This Tool Works
The lookup reads the date code each manufacturer prints in its serial numbers. A. O. Smith, Rheem/Ruud/Richmond and Bradford White rules come from those manufacturers' own documents. State, American, U.S. Craftmaster, Whirlpool and GE rules come from independent inspector guides that agree with each other, so those results carry a “check the rating plate” note. A serial that fits no published pattern, or that decodes to a future date, returns no date. Age counts from the middle of the manufacture month to today. Lifespans come from the U.S. Department of Energy and A. O. Smith.
- A. O. Smith — Service Guide for Contracted Service Providers, July 2024 (How to Read the Serial Number, p. 9)
- A. O. Smith — When to Repair or Replace Your Water Heater
- A. O. Smith — How Long Do Water Heaters Last
- Rheem Technical Service Bulletin 1207 — How to Locate and Read Rheem/Ruud/Richmond Serial Numbers
- Rheem — How to Locate and Read Your Rheem Water Heating Serial Numbers
- Bradford White — My Water Heater (serial number date code chart)
- Bradford White — Determining the Age of a Water Heater (production number length, OA serials)
- Bradford White — Gas-Fired Water Heater Installation and Operation Manual 238-51007-00R (relief valve, draining, anode, scald)
- U.S. Department of Energy — Energy Saver Guide 2022 (water heater life, draining sediment, 120°F)
- U.S. Geological Survey — Hardness of Water
- City of Grand Rapids — 2025 Average Water Analysis, Lake Michigan Filtration Plant
- InterNACHI — Water Heater Dating Chart (State, American, Whirlpool, GE, U.S. Craftmaster)
- Building-Center.org — State water heater age (third-party guide)
- Building-Center.org — Whirlpool water heater age (third-party guide)
- Building-Center.org — GE water heater age (third-party guide)
General information for Grand Rapids-area properties, reviewed October 24, 2026. Rules, rates and programs change; the linked source's current version controls. Dates come from published serial formats; the manufacturer's own records control. Follow the instruction manual for your model when it differs from the steps here.
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