How Old Is My Water Heater? Read the Serial Number

Most homeowners can't say how old their water heater is. That's normal: it sits in a closet or a garage corner and works quietly until the morning it doesn't. But its age is the single most useful thing to know about it, because age tells you whether to keep maintaining it or start planning to replace it. The good news: the answer is printed on the tank. You just have to know how to read it.

Where to find your water heater's age

Go to the tank and find the rating label, the sticker or metal plate on the side, usually at eye level or a little below. It lists the model number, the serial number, and the capacity.

1. Look for a printed date first. Some labels simply say when the heater was made. If yours does, you're done.
2. Otherwise, find the serial number. On most brands, the manufacture date is coded into its first few characters. The next section shows how to read the common ones.
3. Snap a photo of the whole label while you're there. You'll want the model and serial number again for warranty claims, repairs and replacement quotes. (More on that below.)

Can't reach the label, or it's faded? The date often turns up in your home inspection report, the seller's disclosure, an installer's sticker on the tank, or the receipt if the heater was replaced after you moved in.

How to read the serial number, by brand

Each manufacturer uses its own code. These are the common patterns. If your serial doesn't fit, or you want certainty, give the serial number to the manufacturer: their lookup or support line is the final word.

Rheem and Ruud

On many Rheem and Ruud tanks, the first four digits are the month and year:

• 0316xxxxxx = March 2016
• 1109xxxxxx = November 2009

If your serial starts with letters instead of four digits, it uses a different format. Check with Rheem using the serial number rather than guessing.

A.O. Smith and State

On newer A.O. Smith and State tanks, the first two digits are the year and the next two are the week:

• 1719xxxxxxx = 2017, week 19 (mid-May)

Older units used a letter-based code. If your serial starts with a letter, A.O. Smith can read it for you.

Bradford White

Bradford White uses two letters at the start of the serial number: the first is the year, the second is the month.

Month letters: A (January), B, C, D, E, F, G, H, J, K, L, M (December). There's no I.

Year letters repeat every 20 years and skip I, O, Q, R, U and V:

So a serial starting SC was made in March 2018. Because the letters repeat, use common sense (a tank that looks new isn't from 2004) or check Bradford White's "My Water Heater" page, which explains the code and has a warranty lookup by serial number. Bradford White tankless units may use a different format.

American and Whirlpool

On American Water Heater tanks (which have also been sold under the Whirlpool name), the first two digits are the year and the next two are the week: 0906xxxxx = 2009, week 6.

Any other brand

Search for "[brand] water heater serial number date" on the manufacturer's own site, or call their support line with the serial number. Avoid random "age decoder" sites. Many of them disagree with each other.

How long does a water heater last?

A tank water heater commonly lasts about 8 to 12 years, and electric tanks often run a little longer. Hard water, skipped maintenance and a heater that's undersized for the household shorten that. Yearly flushing and a sensible temperature setting help it go longer. Tankless heaters usually last well beyond a tank.

Age tells you when to plan, not when it will fail. A 10-year-old tank in good shape can keep going; a 6-year-old one with warning signs might not.

Signs your water heater is near the end

Start planning a replacement if you notice:

• Rusty or discolored hot water (and only the hot side)
• Rumbling or popping as it heats, usually sediment built up in the bottom
• Moisture, drips or rust at the base of the tank
• Running out of hot water sooner than you used to
• An age at or past the usual range, especially past the end of its tank warranty

A leak at the base of a tank usually can't be repaired. That's the one to act on quickly, before it becomes a floor and drywall problem.

What to do once you know its age

Once you know the age, put it to work:

• Write it down with the model and serial number. Our guide to organizing home warranties, receipts and manuals shows a simple way to keep this kind of record where you can find it.
• Check the warranty. Tank warranties often run 6 to 12 years. The length is usually on the label or in the manual. A heater that fails inside its warranty may be partly covered, but only if you can show the dates.
• Flush it once a year. Draining sediment is the main maintenance a tank needs (how to flush a water heater, step by step). It's part of our new homeowner maintenance checklist. Fall is a good time to do it, alongside the heating service and the rest of the fall jobs in our seasonal home maintenance checklist, before winter puts the heater under its heaviest load. While you're at it, check the furnace filter too (how often to change an HVAC filter).
• If it's in the 8 to 12 year range, start saving and get a quote or two now, while you can choose calmly instead of in an emergency.

Never wonder again

In three years you won't remember the answer. That's the mental load of homeownership: a house has dozens of things like this, and nobody can hold them all in their head.

HouseSpouse keeps it for you. Snap a photo of the label into a note under Appliances and type the age and serial number into the note, so they're one search away. Or just mention the model in chat and it's saved to your notes. Add the warranty and link it to the heater, so you know exactly when coverage ends. And for tank water heaters, its built-in plan can include a yearly flush and nudge you when it's due. Not sure what a rumble or a rust spot means? Send a photo to the built-in assistant and ask.

Want a reminder app for every system, not just the water heater? Here are the best home maintenance apps.

Your two-minute task for today: go read the label, and give your water heater a birthday.