Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
Nobody asks how old their water heater is out of curiosity. The question comes up when it has started to leak, when a home inspection flags it, when an insurer asks, or when somebody is trying to work out whether to repair it or replace it. This page gets you to a defensible date: find the rating plate, record the brand, the model number and the serial number, photograph the plate, and then get the date from the one organisation that actually knows it. On many units the date is simply printed on the plate and you are finished in five minutes. It is only when the plate gives you a serial number and nothing else that the rest of this page matters.
What this page will not do is hand you a decode table for every brand, and the reason is worth stating plainly. A date code is a manufacturer's private scheme, and the only correct version of it is the one the manufacturer publishes. Rheem and Bradford White both publish theirs on their own websites, so this page can cite them and does. AO Smith publishes no scheme at all, only a lookup that takes your serial number and returns the date, and every AO Smith decode table returned by searching on 29 July 2026 was a third-party site. Those third-party tables did not agree with each other about which digits carry the year, which is exactly the failure mode this site exists to avoid. If your brand has not published a scheme, the honest answer is the manufacturer's own lookup or a telephone call, and that is what this page tells you to do.
Safety
DO NOT TOUCH THE VENT PIPE ABOVE A WATER HEATER THAT BURNS GAS.
The vent pipe is very hot during operation and can burn you.
Necessary equipment
| Item | Note |
|---|---|
| Flashlight | The print on a rating plate is small and the space is usually dark. |
| Camera or phone | Use this to make a photograph of the rating plate. |
| Pen and paper | Use these to record the numbers from the rating plate. |
| Dry cloth optional | Use this to clean dust from the rating plate. |
Find the rating plate
Estimated 3 min to 6 min
DO NOT MOVE THE WATER HEATER TO READ THE PLATE.
A full tank is very heavy and can crush your foot.
- Find the rating plate on the water heater.2mReport a problem with step 1, Find the rating plate
- The rating plate is a label on the outer surface of the tank.
- Bradford White tells the reader to find the rating plate first.
- A tankless unit carries the plate on the front or on the right side.
DO NOT USE A WET CLOTH ON THE RATING PLATE.
Water makes the printed label unreadable.
- Clean dust from the rating plate with a dry cloth.<1mReport a problem with step 2, Find the rating plate
- Point the flashlight at the rating plate from one side.<1mReport a problem with step 3, Find the rating plate
- Light from one side makes the stamped characters legible.
- Light from the front causes a reflection.
Record the numbers
Estimated 3 min to 5 min
- Write the brand name from the rating plate.<1mReport a problem with step 1, Record the numbers
- The brand on the plate can be different from the brand on the shop receipt.
- Write the model number from the rating plate.<1mReport a problem with step 2, Record the numbers
- Write the serial number from the rating plate.1mReport a problem with step 3, Record the numbers
- Copy each character exactly.
- The letter O and the number zero are easy to confuse.
- The letter I and the number one are also easy to confuse.
DO NOT HOLD THE CAMERA TOO NEAR THE PLATE.
A reflection from the flash makes the numbers unreadable.
- Make a photograph of the full rating plate.<1mReport a problem with step 4, Record the numbers
- The photograph keeps the data after the label becomes unreadable.
- Make a second photograph that shows the water heater and the room.
Find the date of manufacture
Estimated 12 min to 26 min
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
Source: How to Locate and Read your Rheem Water Heating Serial Numbers · tier 1 · accessed 2026-07-29
Source: How to Locate and Read your Rheem Water Heating Serial Numbers · tier 1 · accessed 2026-07-29
Source: My Water Heater - warranty, age and serial number location · tier 1 · accessed 2026-07-29
Source: My Water Heater - warranty, age and serial number location · tier 1 · accessed 2026-07-29
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
- Look on the rating plate for a printed date of manufacture.1mReport a problem with step 1, Find the date of manufacture
- Many plates print the date in full.
- If the plate gives the date, do not use the serial number at all.
- A date near a warranty statement is usually the date of manufacture.
- If the plate gives no date, open the website of the manufacturer.1mReport a problem with step 2, Find the date of manufacture
- Use the brand name that is on the rating plate.
- Do not use a decode table from a third party.
- Give your serial number to the lookup tool of the manufacturer.2mReport a problem with step 3, Find the date of manufacture
- Bradford White operates a lookup of this kind for its own units.
- AO Smith operates a lookup of this kind and publishes no date code.
- The lookup gives the date for your unit and not for a model family.
- If the manufacturer publishes a date code, apply that code to your serial number.3mReport a problem with step 4, Find the date of manufacture
- Rheem publishes that its serial number has ten digits.
- Rheem publishes that digits 1 and 2 give the month and digits 3 and 4 give the year.
- Bradford White publishes that the first two characters give the year and the month.
- Each year letter of Bradford White gives two possible years.
- The two years are twenty years apart.
- Use the condition of the unit to select between the two years.
- If no published code applies, telephone the manufacturer with your serial number.4mReport a problem with step 5, Find the date of manufacture
- The telephone number is on the rating plate or on the website.
- Do not accept a date from a source that is not the manufacturer.
- Write the date of manufacture and its source in your records.1mReport a problem with step 6, Find the date of manufacture
- Write the method that gave you the date.
- A date from a lookup of the manufacturer is stronger than a date from a code.
After the job
Estimated 2 min
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
- Keep the photograph and the numbers with your home records.1mReport a problem with step 1, After the job
- An insurer or a plumber will ask for these data.
- The date of manufacture is not the same as the date of installation.
- Do not use the age alone for a decision about a replacement.<1mReport a problem with step 2, After the job
- The manufacturer gives the expected service life for your model.
- A qualified plumber must examine the condition of the unit.
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- water heater
- Also called: hot water heater, hot water tank, hot water cylinder, boiler, geyser, immersion heater
- rating plate
- Also called: data plate, nameplate, name plate, spec plate, specification label, sticker on the water heater, serial number sticker
- date of manufacture
- Also called: manufacture date, date code, build date, when was my hot water heater made, year of manufacture
- serial number
- Also called: serial no, SN, water heater serial number age, serial number decoder
When to use a professional
This page reads a label. It does not open, move, drain or disconnect anything.
Speak to a qualified plumber if you find water below the water heater. Speak to a qualified plumber also if you find rust on the tank or on the connections at the top. An old tank that leaks does not become safe again.
Do not remove any cover or panel to look for a serial number. If you cannot see the rating plate from a standing position, stop. A qualified plumber can read it during a service visit.
A qualified plumber must make the decision about a replacement. The age of the unit is only one of the facts in that decision. The condition of the tank and of the connections is more important than the date.
Common questions
How old is my water heater?
Start with the rating plate on the side of the unit, because a lot of plates simply print the date of manufacture and you are done. If yours only carries a serial number, the date is inside that serial number according to a scheme your manufacturer sets, and the reliable way to get it is the manufacturer's own lookup or a phone call. Bradford White and Rheem both publish their schemes on their own websites, so those two you can read yourself. Whatever route you take, write down which one gave you the date, because a date from the manufacturer is worth more than a date you decoded.
Is there a universal water heater serial number decoder?
No, and the ones that claim to be are compilations someone assembled from other people's compilations. Each manufacturer picks its own scheme, changes it, and is under no obligation to tell anyone outside its dealer network. When we checked AO Smith on 29 July 2026, the third-party tables in the search results disagreed with each other about whether the year sat in the first two digits or the third and fourth. A table that is wrong about the decade will tell you your water heater is ten years old when it is thirty, which is the sort of error that gets a leaking tank left in place. That is why this page cites two manufacturers who publish, and sends you to the manufacturer for everything else.
My Bradford White serial starts with a letter. What year is that?
Bradford White publishes the answer, and it has a catch worth knowing about. The first character is the year and the second is the month, and the letters skip I, O, Q, R, U and V. The catch is that the year letters run on a twenty-year cycle, so A means 2004 or 2024, B means 2005 or 2025, and so on. The letter on its own cannot tell you which of the two it is. If the unit is obviously not two years old, it is the earlier year, and if you want it settled properly, Bradford White's own lookup form takes the whole serial number and returns the date.
How long does a water heater last?
This page does not publish a number for that, and the omission is deliberate. Service life depends on the model, the water chemistry where you live, whether the anode rod was ever replaced and how hard the unit has been worked, and no figure that ignores all of that is worth printing next to a decision about replacing an appliance. Your manufacturer publishes an expected service life and a warranty period for your specific model, and those are the numbers that mean something. A plumber looking at the actual tank will tell you more than any average ever could.
Why won't this page just print the decode table for my brand?
Because for most brands there is no table we could print that we would be willing to stand behind. If a scheme only exists on third-party sites, it is unverified by definition however confident those sites sound, and independent-looking sites copy each other constantly. Where a manufacturer does publish, we cite the manufacturer's own page so you are reading the current version rather than a snapshot that may already be stale. The tables move; the manufacturers' pages get updated.
Is the date of manufacture the same as the date it was installed?
No, and the gap can be substantial. A water heater can sit in a distributor's warehouse or a builder's merchant for a year or more before anyone fits it, so a unit made in March can easily have been installed the following spring. Warranty periods usually run from the date of installation or purchase rather than manufacture, which is why an installer's invoice is worth keeping alongside the photograph of the plate. For working out how old the appliance is in service, the manufacture date is the conservative answer and the safer one to plan around.
Related procedures
- How to find and record the model and serial number of every appliance in the house
- How to read a tire sidewall and find out how old your tires are
- How do I read the label on my hot water heater and figure out what the numbers mean
- How do I decode the date code on my appliance and find out how old it is
- How do I find the date on my smoke alarm and how old can it be before I replace it
- Where is the water under my hot water heater coming from, and does it mean I need a new one?
- Find the date code on a vehicle battery and work out how old it actually is
- How to read the label on a power tool and understand what the numbers mean
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1How to Locate and Read your Rheem Water Heating Serial Numbers
- Tier 1My Water Heater - warranty, age and serial number location
- Tier 1How to read the serial number date code reference chart?
- Tier 1Resources - warranty lookup
Revision history
Current version 1 · updated 2026-07-29 · next review due 2027-07-29
- v1 · 2026-07-29First draft. The date code publishes as consult-manufacturer, because a scheme that exists only on a third-party site is unverified by definition. Two exceptions are cited as verified because the manufacturers publish them on their own domains: Rheem's ten-digit format and Bradford White's first-two-character format, including the twenty-year ambiguity in the Bradford White year letter that the third-party rehosts drop. AO Smith publishes no scheme and is cited for that negative fact. No step opens, moves, drains or disconnects anything.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.