How long do water heaters last?

What the published numbers say

Estimates vary a little depending on who's counting:

• Conventional tank heaters: 6 to 12 years on InterNACHI's life expectancy chart, with about 10 years described as typical.
• Tank heaters in DOE research: a Department of Energy Building America study used an estimated life of 13 years.
• Tankless heaters: the same DOE study used 20 years. InterNACHI's chart lists on-demand heaters at about 10 years, so treat 20 as a best case that depends on regular descaling.

No chart can tell you exactly when your heater will fail. They tell you when to start paying attention.

Find your heater's age

The label on the side of the tank lists the model and serial number. Some labels print the manufacture date. If yours doesn't, the serial number usually encodes the month and year, and each brand uses its own format. A photo of the label lets a plumber read it for you.

If the heater came with the house, the build year is a rough guide. A home built 12 years ago that still has its original tank is living on borrowed time.

What shortens a water heater's life

InterNACHI lists several factors that decide where in that range a heater lands:

• Hard water. Minerals settle as sediment and scale, and heaters in hard-water areas have shorter lives. Kuna, Idaho, for example, rates its city water as hard at about 8 grains per gallon (see our Kuna page).
• Corrosive water. Some water dissolves metal. Norwell, Massachusetts treats its naturally corrosive groundwater to raise the pH before it reaches homes (see our Norwell page).
• The anode rod. This metal rod corrodes so the steel tank doesn't. Once it's used up, the tank itself starts to rust. Bigger or thicker anodes protect longer.
• Heavy use. More hot water means more heating cycles and more wear.
• Build quality. Cheaper models generally don't last as long. A longer warranty is a decent hint at a sturdier tank.
• Installation. InterNACHI says heaters should be installed upright in well-ventilated areas, and that poor ventilation can shorten a heater's life.

How to help it last longer

A. O. Smith recommends checking the temperature and pressure relief valve once a year and inspecting the anode rod, which is replaced when it's worn. A DOE and Oak Ridge National Laboratory remodeling guide suggests checking the anode every three to five years in normal water, and clearing sediment from the bottom of the tank.

Flushing a few gallons out of the drain valve once a year helps keep sediment from building up. If an older tank has never been flushed, ask a plumber first. Loosened sediment can clog the drain valve so it won't close.

Signs it's near the end

• Rusty or discolored hot water, especially if the cold water is clear
• Water pooling around the base, or a damp ring under the tank
• Popping or rumbling that keeps getting louder
• Hot water that runs out much faster than it used to
• Repairs that keep coming back

A leak from the tank body itself can't be repaired, and the heater has to be replaced. A failed part on a sound tank, like a thermocouple, element or thermostat, usually can be.

Local pages mentioned

• Windsor, CO
• Erie, CO
• Kuna, ID
• Norwell, MA