How Long Does a Water Heater Last?

A tank water heater often lasts somewhere around 8 to 12 years, and a tankless unit often lasts 15 years or more with regular maintenance. Water quality, water pressure, and whether it has been flushed and serviced make a bigger difference than the brand.

How to find out how old yours is

The age is almost always hiding in the serial number on the label on the side of the tank or unit. Manufacturers use different formats, but most encode the year and month or week of manufacture somewhere in the first few characters.

• Find the label. It is usually a sticker on the side of the tank near the top or near the controls. Use a flashlight and take a photo so you can read it comfortably.

• Look for a date in the serial number. Some brands start with a letter for the month and two digits for the year. Others start with a four-digit year and week. If the format is not obvious, search the brand name plus "serial number age" or call the manufacturer with the number.

• Check the label for a manufacture date. Some units print the date in plain text, which saves you the decoding.

• Look for install records. A plumber's sticker on the tank, a permit, or your home inspection report may list the install date. Manufacture and install dates are usually close.

Once you know the age, write it down somewhere you will find it later. Age is the single most useful number when you are deciding whether a repair is worth it.

Signs a water heater is near the end

• Water pooling under the tank with no wet fittings above it. That usually means the tank has rusted through. See why a water heater leaks.
• Rusty or discolored hot water while the cold water runs clear, which can mean the inside of the tank is corroding.
• Rumbling, popping, or banging when it heats. That is often sediment on the bottom of a tank. Flushing can help, but on an old unit it usually means years of buildup.
• Less hot water than it used to make, or water that is never quite hot enough.
• Rust on the outside of the tank, especially around the fittings on top or the base.
• Repairs piling up. One fix on a young unit is normal. Several in a year on an old one is a pattern.

What makes a water heater last longer

• Flush it once a year (if you have a tank). Draining a few gallons through the drain valve clears sediment that settles on the bottom. If you have never flushed an older tank, go easy, since years of sediment can clog an old drain valve.

• Check the anode rod every few years (if you have a tank). The anode rod corrodes so the tank does not. Once it is used up, the tank starts to go. Checking it every 3 to 5 years is a common rule of thumb, sooner if you have hard or softened water.

• Keep water pressure in a normal range. High pressure strains the tank and relief valve. A $10-$15 gauge on an outdoor faucet tells you where you stand. If you have a pressure reducing valve or check valve, an expansion tank helps absorb the pressure rise when water heats.

• Descale it (if you have a tankless unit). Tankless units build scale inside the heat exchanger, especially with hard water. Many manufacturers recommend flushing with a descaling solution about once a year. Check your manual.

• Set the temperature sensibly. Around 120°F is a common recommendation for households without special needs. Hotter water speeds up scale and is a scald risk.

Repair or replace?

A simple way to think about it: if the unit is well under its expected age and the repair is a few hundred dollars, repair it. If the unit is near or past the end of that range and the repair is a meaningful fraction of a new install, put the money toward a replacement instead.

• Always replace if the tank itself is leaking. Tanks cannot be patched.
• Usually repair a relief valve, drain valve, thermocouple, or heating element on a younger unit. These are cheap parts that do not shorten its life.
• Lean toward replacing if it is past about 10 years and needs anything beyond a small part, or if it is the second or third repair in a short time.

Replacing on your own schedule is cheaper than replacing in an emergency. You can get two or three quotes, choose the size and type you want, and avoid paying for water damage cleanup on top of the heater.

Tank vs tankless lifespan

Tankless water heaters often last longer than tanks because there is no large vessel of water sitting and corroding. They cost more up front, and they need regular descaling to reach that longer life, especially in hard water areas. A tank is cheaper to install and simpler to service, but it will likely need replacing sooner. If your current tank is near the end, it is a good time to compare both, but the right answer depends on your household, your fuel type, and what it costs to run gas or electrical to a new unit.