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How long do water heaters last, and how to tell how old yours is
A tank water heater typically lasts 6 to 12 years. Tankless units last about twice as long. The label on yours says how old it is, once you know how to read it, and a few signs tell you when it is close to the end.
Typical lifespan by type
| Type | Typical life | Why it ends |
|---|---|---|
| Tank, gas or electric | 6 to 12 years | The tank rusts from the inside once the anode rod is used up; sediment burns the bottom. |
| Tankless (on demand) | About 20 years | Scale builds in the heat exchanger; parts are replaceable, so it is serviced rather than replaced. |
| Heat pump (hybrid) tank | 10 to 15 years | Same tank as a standard unit, with a compressor on top. |
Ranges from the InterNACHI life expectancy chart and the U.S. Department of Energy. Hard water, high temperature settings and a used up anode rod shorten them.
How to find the age of your water heater
Look at the rating plate on the side of the tank. Some makers print the manufacture date plainly. Most hide it in the serial number:
- Rheem, Ruud and Richmond: the first four digits are the month and year, MMYY. A serial starting 0318 was made in March 2018.
- A.O. Smith, State, American and Reliance (since about 2008): the first two digits are the year and the next two the week. 1532 is the 32nd week of 2015.
- Bradford White: two letters, the first for the year and the second for the month, on a letter cycle that repeats every 20 years. Bradford White publishes a serial number lookup that decodes it.
- Anything else: the maker’s support page usually has a lookup, and the Housemap label scan reads the plate and works out the age for you.
Signs a water heater is near the end
- Rust colored hot water, or rust on the tank bottom or around the fittings.
- Rumbling or popping while it heats: sediment on the bottom of the tank.
- Water on the floor around the base, even a little, that is not from a fitting.
- Lukewarm water, or hot water that runs out faster than it used to.
- It is past 10 years old. Plan the replacement before it fails on a Sunday.
How to make one last longer
- Flush a few gallons from the drain valve once a year to clear sediment. Twice a year with hard water.
- Check the anode rod every three years and replace it when it is mostly gone; it is the part that rusts so the tank does not.
- Set the temperature to 120°F. Hotter water speeds scale and the risk of scalding.
- Test the temperature and pressure relief valve once a year: lift the lever, let it run a few seconds, let it close.
- Put a pan with a drain under a tank in a finished space, and a leak alarm on the floor.
Write the date down
Once you know the year, put it where you will find it again: the install date, the model and serial, the warranty end date (tank warranties run 6, 9 or 12 years) and the date of the last flush. Housemap reads the label from a photo, keeps the age and the warranty date on the equipment card, checks the federal recall database, and reminds you before the flush is due. See the home maintenance log guide.
Questions
How long does a gas water heater last?
About 6 to 12 years for a tank unit. Gas and electric tanks last about the same; the tank is what fails. Tankless gas units last about 20 years with regular descaling.
Should I replace a water heater before it fails?
If it is past 10 years and shows any sign (rust, rumbling, moisture at the base), yes. A planned replacement costs less than an emergency one and avoids a flooded floor.
How do I tell the age of my water heater from the serial number?
Rheem prints the month and year as the first four digits. A.O. Smith and State use year and week as the first four digits. Bradford White uses two letters; its website decodes them. Or scan the label with Housemap.
How often should a water heater be flushed?
Once a year, and twice a year if your water is hard. Flushing clears the sediment that insulates the burner from the water and shortens the tank’s life.
Sources
Related guides
Scan the label. Know the age.
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