How Long Does a Water Heater Last?
A tank water heater lasts 8 to 15 years; most get replaced at 10 to 12. Tankless runs 15 to 20+. The anode rod decides which end you land on.
A conventional tank water heater lasts 8 to 15 years, and most get replaced between year 10 and 12. Rheem gives its own tanks an 8-to-12-year average; InterNACHI puts the range at 6 to 12. A tankless unit lasts 15 to 20 years or more — 25 to 30 if it is descaled every year.
The single thing that decides where a tank lands in that range is the anode rod, and almost nobody touches it.
How long does a tank water heater last?
8 to 15 years, with 10 to 12 the realistic middle. A tank fails from the inside: the steel corrodes until it perforates, and then it leaks. It rarely just stops heating. That is why age matters more for a water heater than for almost anything else in the house — a late replacement means a flooded room, not a cold shower.
What tends to go wrong, and when:
| Age | What fails | What it means |
|---|---|---|
| Years 1–5 | Thermocouple (gas) or heating element (electric) | A $150–$250 fix. Not a sign the tank is failing. |
| Years 6–9 | The anode rod is spent | Replace it now ($20–$40 part) or corrosion starts on the tank itself. |
| Years 10–12 | Sediment build-up, rumbling, efficiency drop, early corrosion | The window where most tanks get replaced. |
| Years 13+ | Past typical life | Tank failure is a matter of when. It fails by leaking. |
If you don't know how old yours is, the serial number on the rating plate carries the build date — Rheem and Ruud put the month and year in the first four digits, A.O. Smith uses the year and week.
How long does a tankless water heater last?
15 to 20 years or more, and 25 to 30 with yearly maintenance — roughly double a tank. There is no stored tank of water sitting against steel, so the main corrosion path is gone. Tankless units are also more repairable: the heat exchanger, igniter, and flow sensor are all serviceable parts, where a leaking tank is simply done.
The catch is scale. Hard water deposits minerals on the heat exchanger, which makes it run hotter and eventually fail. A tankless unit needs to be descaled once a year (more in very hard water) — skip that and you can lose a decade off its life. Factor the descaling into the tank-vs-tankless decision: the longer life only holds if you keep up with it.
What shortens a water heater's life?
| Factor | Effect |
|---|---|
| Hard water | Sediment in a tank, scale in a tankless — the biggest single factor for both |
| A spent anode rod (tank) | Once it's gone, the tank corrodes directly. This is the usual reason a tank dies at 10 instead of 18. |
| No annual flush (tank) / descale (tankless) | Sediment and scale accumulate and insulate the heat source |
| Temperature set above 130°F | Faster corrosion and scale; 120°F is enough for most homes |
| A closed plumbing system with no expansion tank | Pressure spikes on every heating cycle stress the tank seams |
| An undersized unit run at capacity | Constant full-load cycling wears components faster |
Does the brand matter?
Not much. Rheem, A.O. Smith, and Bradford White tanks all last about 8 to 12 years, and they are built to similar standards. The clearest signal of a longer-lasting unit is the warranty length — a 9- or 12-year tank usually has a thicker anode rod and a better glass lining than the 6-year builder-grade version, and that is most of what separates them.
Water hardness and whether the anode rod is ever replaced will change a tank's life by more years than the choice of brand ever will.
The one thing that doubles a tank's life
Replace the anode rod. It is a sacrificial metal rod inside the tank that corrodes so the steel doesn't. It is typically spent within about five years, costs $20 to $40, and takes an hour to swap. Check it every 2 to 3 years and replace it when more than half is gone.
Almost nobody does this — which is precisely why the average tank lasts about 10 years instead of the 18 to 20 it is capable of. If you do one thing for your water heater, it is this. Here is how the anode rod works and how to check it.
How to make a water heater last longer
Beyond the anode rod, the upkeep is short and cheap:
- Flush the tank once a year. Draining a few gallons from the bottom valve clears the sediment that insulates the burner and holds heat against the steel. Twenty minutes.
- Descale a tankless unit every year — every 6 months in very hard water. This is the tankless equivalent of the anode rod: skip it and the heat exchanger fails early.
- Set the thermostat to 120°F. It is hot enough for a house, and every 10 degrees above that measurably speeds up corrosion and scale.
- Add an expansion tank if your home has a pressure-reducing valve or a check valve (a "closed system"). It absorbs the pressure spike on every heating cycle instead of letting the tank seams take it. Often now required by code on a replacement anyway.
- Soften hard water. A water softener is the single biggest lever if your water is above ~7 grains per gallon — it protects the heater, the pipes, and every other appliance.
- Insulate the tank and the first few feet of hot pipe. Less strain from reheating, lower bills.
When to replace, and when to wait
Past 10 to 12 years, plan the replacement — but you don't have to do it the day the tank turns 10. A tank that is dry at the base, quiet, and heating normally can keep going while you shop and schedule. If it has actually failed, whether to repair or replace it comes down to the age and the part.
Replace it now if:
- Water is weeping or pooling at the base — a leaking tank cannot be repaired.
- It rumbles or pops loudly during heating (heavy sediment).
- The hot water runs rusty or smells metallic while the cold runs clear.
- It is over 10 and facing any repair beyond a thermocouple or element.
When the time comes, a like-for-like replacement runs $900 to $2,200 installed — and doing it on your own schedule instead of after a flood is where most of the savings are.
Frequently Asked Questions
How long does a water heater last on average?
A conventional tank lasts 8 to 15 years, and most are replaced between year 10 and 12 — Rheem gives its own tanks an 8-to-12-year average. A tankless unit lasts 15 to 20 years or more, and 25 to 30 with yearly descaling.
Can a water heater last 20 years?
A tank rarely does — past 15 the steel is corroding and a leak can start without warning. A tankless routinely reaches 20 and beyond, because there is no standing tank to rust, as long as it is descaled every year in hard water.
How long do Rheem, A.O. Smith, or Bradford White water heaters last?
About the same — 8 to 12 years for a tank from any of the mainstream brands. Water hardness and whether the anode rod is ever replaced matter far more than the badge. A longer warranty (9 or 12 years vs 6) usually signals a thicker anode rod and a better tank lining.
Should I replace my water heater at 10 years?
Not automatically. A 10-year-old tank that is dry, quiet, and heating normally can keep running while you plan and shop. Replace it now if it weeps at the base, makes rumbling or popping noises, or the hot water runs rusty while the cold runs clear.
Does hard water shorten a water heater’s life?
Yes, for both types. In a tank, minerals settle as sediment that traps heat against the steel and accelerates corrosion. In a tankless unit, scale coats the heat exchanger and forces it to run hotter. A hard-water tank can reach the end of its life several years early.
Sources
- Rheem — Tank vs. Tankless Water Heater Lifespan Comparison — tank 8–12 years; tankless 15–20+ (25–30 well-maintained); anode rod, flushing, descaling as the levers
- InterNACHI — Standard Estimated Life Expectancy Chart for Homes — conventional tank water heater 6–12 years; water softener 20; "mineral content of water can shorten the life expectancy"