Water Heater Guide
Water Heater Model Number & Serial Number Lookup Guide
Decode your water heater’s rating plate in minutes. Additionally, find your manufacture date, warranty info, and unit specs for Rheem, A.O. Smith, Bradford White, American, Rinnai, Noritz, and Navien.
Covers 7 major brands: Rheem, A.O. Smith, Bradford White, American, Rinnai, Noritz, and Navien.
Water Heater Serial Number Lookup & Rating Plates
Every water heater has a rating plate — a metal label attached to the tank. Specifically, this plate contains the model number, serial number, manufacturing date, warranty info, and energy specs. Consequently, knowing how to read these numbers helps you find parts, verify your warranty, and identify your unit’s age. Therefore, use this guide to decode serial numbers for Rheem, A.O. Smith, Bradford White, American, Rinnai, Noritz, and Navien.
Jump to Your Brand
Where to find your rating plate: Look on the side of the tank (usually upper third), or on the front panel for tankless units. Specifically, the serial number and model number are clearly labeled on this metal data plate.
Rheem Water Heater Model Numbers
Generally, Rheem water heaters are known for their user-friendly rating plates, which provide clear information about their manufacture date, size, and capacity. To help you understand these details, here’s how you can interpret the information on both new and older models.
Understanding Serial Numbers on Older Models
Rheem serial numbers encode the manufacture date, but the format depends on when Rheem built the unit. Specifically, older Rheem water heaters (generally pre-2000) use the first four digits to show month and year: the first two digits indicate the month, and the next two indicate the year.
1291A39968 → Rheem manufactured this unit in December 1991 (’12’ for December, ’91’ for 1991).Newer Rheem models, however, use a different format where digits 2–3 represent the week of manufacture and digits 4–5 represent the year. Consequently, if you’re unsure which format applies to your unit, Rheem’s website has a serial number age calculator at rheem.com/how-old-is-my-equipment.
What You’ll Find on the Rating Plate
Here’s a breakdown of the key fields on a typical Rheem rating plate:
Rheem model numbers typically start with letters indicating the type: ‘XR’ for extended recovery, ‘MR’ for mid-recovery, and ‘G’ for gas. Moreover, the numbers that follow indicate the tank’s gallon capacity and BTU rating.
The EF rating shows how efficiently the unit uses energy. Consequently, a higher EF means better efficiency and lower operating costs.
Rheem tests each unit up to the listed maximum working pressure (typically 150 PSI). As a result, the unit should not be operated above this pressure.
Need help with your Rheem? Fast Water Heater Co. is an authorized Rheem service partner throughout Washington, Oregon, and California. View our services
AO
A.O. Smith Model Numbers
Their serial numbers encode the manufacture date using a year-then-week format. Specifically, specifically, the first two digits represent the year of manufacture, and the next two digits represent the week of the year.
Year First, Week Second
9707 → A.O. Smith manufactured this unit during the 7th week of 1997 (mid-February 1997). Similarly, a serial starting with 1512 means the 12th week of 2015 (late March 2015).Locating the Information
Typically, the rating plate sits on the upper portion of the water heater’s side. Look for the serial number — a string of 10 or more digits — and use the first four digits to determine the manufacture date. Notably, A.O. Smith acquired American Water Heater Company in 2006, so many American-branded units follow the same year-week format.
DECODE FORMAT
Digits 1–2 = Year of manufacture | Digits 3–4 = Week of year | Remaining digits = unit identifier
Tip: Additionally, A.O. Smith’s website offers a registration tool where you can enter your serial number to confirm the manufacture date and register for warranty coverage.
Bradford White Model Numbers
Bradford White uses a distinctive letter-based system for serial numbers, where each letter corresponds to a specific year. Notably, this approach differs from the numeric year formats used by other manufacturers.
Year of Manufacture
The first letter of the serial number indicates the year Bradford White made the tank. Importantly, Bradford White recycles the letter sequence every 20 years, so you may need additional context (such as the model number) to determine the decade. You can also use the Bradford White product lookup to verify your unit.
A=1964/1984/2004/2024 B=1965/1985/2005 C=1966/1986/2006 D=1967/1987/2007 E=1968/1988/2008 F=1969/1989/2009 G=1970/1990/2010 H=1971/1991/2011 J=1972/1992/2012 K=1973/1993/2013 L=1974/1994/2014 M=1975/1995/2015 N=1976/1996/2016 P=1977/1997/2017
Month of Manufacture
The second letter indicates the month of manufacture. Consequently, consequently, combining the first two letters gives you both the year and month when Bradford White built the tank.
A=January B=February C=March D=April E=May F=June G=July H=August J=September K=October L=November M=December
GE → Bradford White manufactured this unit in May 2010 (G=2010, E=May).Pressure Rating & Capacity
Bradford White designed each unit for a specific maximum working pressure (MWP). Furthermore, the rating plate also shows the storage capacity in gallons and the first-hour rating (FHR) — the amount of hot water the unit can deliver in the first hour of use.
American Water Heater Model Numbers
American Water Heater Company uses a numeric serial number system that encodes the manufacture date directly. Specifically, As noted above, A.O. Smith acquired American Water Heater in 2006, so newer units follow the same year-week serial format.
Decoding the Serial Number
9817353574 Year: 1998 (first two digits: ’98’)
Week: 17th week of 1998 = mid-April 1998 (digits 3–4: ’17’)
Unit ID: 353574 (remaining digits identify the specific unit)
Where to Find the Rating Plate
On American water heaters, the rating plate is on the upper portion of the tank’s side. Moreover, the label shows the serial number, model number, energy factor, gallon capacity, and input BTU rating.
Digits 1–2 = Year | Digits 3–4 = Week | Remaining = Unit identifier
Note: In cases where your American unit was manufactured after 2006, it may use A.O. Smith’s year-week format. Additionally, some older units used a different format — if in doubt, contact Fast Water Heater Co. for help decoding your serial number.
Rinnai Tankless Water Heater Serial Numbers
Rinnai is one of the most popular tankless water heater brands in North America, and Fast Water Heater installs and services Rinnai units throughout Washington, Oregon, and California. Moreover, Rinnai’s serial numbers follow a clear format that encodes the manufacturing location and date.
How the Serial Number Works
Each Rinnai unit carries a data label that encodes both its origin and production date. Typically, the first character is a letter indicating the manufacturing plant, followed by digits encoding the year and week of manufacture.
Letter = Manufacturing plant | Next 2 digits = Year | Next 2 digits = Week | Remaining = Unit sequence
B1524XXXXX → Plant B, manufactured in the 24th week of 2015 (mid-June 2015).Finding the Model Number
On Rinnai tankless units, the model number appears prominently on the front panel label. Specifically, the model number indicates the BTU capacity — for instance, the RU199iN is a 199,000 BTU condensing unit. Visit rinnai.us to register your product. The letter at the end identifies the fuel type: N for natural gas, P for propane.
Service tip: However, if your Rinnai is displaying an error code alongside a model or serial number issue, Fast Water Heater Co. can diagnose and repair it same-day in most service areas. Book a service call
Noritz Tankless Water Heater Serial Numbers
Noritz is a Japanese-founded tankless water heater brand with a strong reputation for reliability and longevity. Additionally, Fast Water Heater is an authorized Noritz service dealer throughout the West Coast.
How to Read the Data Plate
Look for the data plate on the front of the unit. Noritz maintains a consistent format across all its models for encoding the manufacture date.
First 4 digits = Year and month of manufacture | Note that the period in some serial formats separates the year from the month
1809 → Noritz manufactured this unit in September 2018 (’18’ = year 2018, ’09’ = September).Understanding the Model Number
Specifically, Noritz model numbers indicate the BTU capacity and unit type. For example, NRC98DV is a 9,800 BTU condensing direct-vent unit. Specifically, the DV suffix means direct vent, while OD means outdoor installation.
Note: Furthermore, Noritz model numbers for commercial units typically include a ‘C’ suffix. If your unit’s model number looks unfamiliar, however, our technicians can identify it on-site during a service visit. You can also search your model at noritz.com.
Navien has grown into one of the leading condensing tankless water heater brands in North America. Moreover, Fast Water Heater installs and services Navien units throughout Washington, Oregon, and California. Navien is particularly known for high energy efficiency ratings and smart home compatibility.
Reading the Serial Number
Navien serial numbers appear on the data label on the front of the unit, typically behind the front cover panel. Specifically, the serial number encodes the manufacturing year and production sequence.
First 2 digits = Year of manufacture | Next 2 digits = Month | Remaining digits = Production sequence number
1811 → Navien manufactured this unit in November 2018 (’18’ = year, ’11’ = November).Model Number Breakdown
Navien model numbers indicate the unit type and BTU capacity. For example, NPE-240A2 is a 240,000 BTU condensing tankless unit (A2 = second generation). Additionally, NHB indicates a condensing boiler, while NCB indicates a combi-boiler that handles both space heating and domestic hot water. Navien’s product registration page lets you log your unit for warranty coverage.
Need a Navien installed or serviced? Fast Water Heater Co. is a Navien-trained service partner. As a result, our technicians can handle warranty repairs, annual maintenance, and new installations throughout the West Coast. Call us at (253) 367-2960
About This Guide
This guide was compiled by the service team at Fast Water Heater Co., a licensed water heater contractor serving Washington, Oregon, and California since 1986. Furthermore, our technicians have decoded thousands of water heater serial numbers during service calls, installations, and warranty repairs across all major brands.
Last updated: April 2026 · Reviewed by: Fast Water Heater Co. Service Team · Licenses: WA #FASTWH893K3 · OR · CA
Frequently Asked Questions
Common questions about water heater model numbers, serial numbers, and rating plates.
Can’t Identify Your Water Heater?
Fast Water Heater Co. has served homeowners throughout Washington, Oregon, and California since 1986. Our certified technicians can identify any water heater model, source the right parts, and get your hot water running the same day.
Call before noon for same-day service in most areas