Short answerA tank-style gas water heater in Southeast Michigan typically lasts 8 to 14 years. The anode rod inside the tank is consumed by the area's hard water in roughly 5 to 8 years, and once it is gone the steel tank starts to corrode. Rusty hot water, rumbling from sediment, moisture at the base and a unit past 10 years are the signs to replace before it leaks.
What actually wears out
A tank water heater is a steel cylinder with a thin glass lining on the inside, a burner or elements to heat it, and a sacrificial anode rod hanging down from the top. The glass lining always has microscopic flaws, and the anode rod, a magnesium or aluminum rod that corrodes more readily than steel, protects those flaws by giving the water something else to attack. As long as the anode has material left, the tank is protected. When the anode is consumed down to its steel core wire, the water goes after the tank, and the tank's remaining life is measured in a few years.
That is why the question "how long does a water heater last" has a mechanical answer: as long as the anode protects it, plus a few years. In soft water an anode can last 10 years. In the water around here it does not.
Why Washtenaw County water shortens the clock
Municipal water in Ann Arbor, Ypsilanti and the surrounding communities served by the Ann Arbor and Ypsilanti Community Utilities Authority systems runs moderately hard, around 8 to 12 grains per gallon depending on the source and season. Well water in the townships, Augusta, York, Lodi, Salem, Superior and out toward Whittaker and Willis, is routinely 20 to 30 grains and sometimes higher, with iron on top of the hardness. Hard water does two things to a water heater. It accelerates anode consumption, and it drops calcium carbonate sediment to the bottom of the tank every time the water is heated.
Sediment is the second killer. A few inches of mineral scale on the bottom of a gas tank insulates the water from the burner, so the burner runs longer and the steel under the sediment overheats. That is the popping and rumbling you hear from an old water heater; water trapped under the scale is boiling. The overheated steel fatigues the glass lining, and the tank fails from the bottom. On well water without a softener, we see tanks fail at year 7. On softened water with the anode checked and replaced once, we see them reach 15.
Typical lifespans by type
- Atmospheric gas, standard 40 or 50 gallon. 8 to 12 years on municipal water, 6 to 10 on hard well water, 12 to 15 with a softener and anode replacement. This is most of what sits in basements across Ypsilanti, Westland and Canton.
- Power-vented gas. Similar tank life, but the blower motor and pressure switch add failure points at year 8 to 12 that are repairable.
- Electric tank. Often 10 to 15 years because there is no burner to overheat the bottom, though elements fail and get replaced along the way.
- Tankless gas. 15 to 20 years with annual descaling, which in this water is not optional. Skip the descaling and the heat exchanger scales up within five years.
- Heat pump water heaters. Too new in this market to have a long local track record; the manufacturers rate them similar to electric tanks.
Signs it is time
- Age past 10 years. Check the serial number on the data plate; the manufacture date is encoded in it, and the format varies by brand. Past 10 years in this water, the tank is living on whatever anode is left.
- Rust-colored hot water. Hot only, not cold. The cold side being clear rules out the supply; the hot side being orange means the tank interior is corroding. Flush it once to rule out sediment, and if it comes back, the tank is on its way out.
- Rumbling, popping or kettling. Sediment on the bottom. A flush helps if it is caught early; years of accumulation hardens into a layer that will not drain and is a sign the bottom has been overheating.
- Moisture or rust at the base. Weeping at the bottom seam, rust staining on the jacket near the floor, or a damp spot under the unit that is not condensation. Once the tank body leaks, replacement is the only option; our leaking water heater guide covers how to tell.
- Corroded fittings on top. Green or white crust at the inlet and outlet is a fitting problem on its own, but on an old tank it usually means the inside looks worse.
- Not enough hot water any more. Sediment reduces capacity and a tired burner heats slower. A 50-gallon tank that behaves like a 30 is telling you something.
- A pilot or gas control problem on an old tank. Repairing the control valve on a 13-year-old tank is money into a vessel that is about to leak.
Repair or replace
Under 8 years: repair. Thermocouples, gas controls, elements, thermostats, drain valves and TPR valves are all reasonable fixes on a tank with life left, and a water heater repair call is the right first move. If the anode has not been checked, this is the time; replacing it on a mid-life tank can add years.
Between 8 and 12: repair cheap things, think hard about expensive ones. A thermocouple, yes. A gas control valve or a power-vent blower, maybe, depending on the condition of the tank and whether there is rust at the fittings.
Past 12, or any age with a tank leak: replace. Under typical market pricing, a standard gas tank replacement in our area lands in the low-to-mid four figures installed, and a repair that costs a third of that on a tank that will leak within two years is not a good use of money. We say so when we see it.
Replacing on your schedule instead of the tank's
The water heater that fails on its own does it at 6 a.m. on a Monday, floods the basement, and leaves the family without hot water until a unit can be sourced and installed. The water heater that gets replaced because it hit 11 years and showed rust at the base gets done on a weekday afternoon of your choosing, with time to decide whether a 50-gallon makes more sense than the 40 that was there, whether a power-vent solves the orphaned-chimney problem, and whether this is the moment to go tankless. Our water heater installation estimates are free and include the permit and inspection, a new TPR valve, an expansion tank where the water system needs one, and hauling the old tank out. In the meantime, a leak alarm on the floor next to the tank is the cheapest insurance in the house.
Keeping a tank alive to the long end of its range comes down to two things, a flush to clear sediment and an anode check every few years, which we cover in the water heater maintenance guide.