How long do water heaters last in Arizona's hard water?

Arizona water heater lifespan: the official figures

The U.S. Department of Energy’s Energy Saver guide (2022) says most storage water heaters last 10 to 15 years, while tankless water heaters can last more than 20. An older Department of Energy fact sheet gives the same split and explains why: tankless heaters don’t store water, so they are less subject to corrosion. We found no federal, state or maker figure for Arizona specifically, so treat 10 to 15 years as the range for a tank heater here too.

What Arizona does have is hard water. The City of Phoenix’s 2025 annual water quality report puts Phoenix hardness at 10 to 17.6 grains per gallon and says hard water can cause scaling in pipes and water heaters. Our page on hardness in each Valley city has your own city’s figure.

How Valley water builds sediment in a tank

A. O. Smith’s guide for its electric heaters explains it: minerals in tap water form lime deposits on the heating elements and sediment in the bottom of the tank, and the amount depends on how hard your water is. The Department of Energy adds that sediment gets in the way of heat transfer and lowers the heater’s efficiency.

A. O. Smith’s advice for very hard water is to remove and check the heating elements whenever you drain the tank, and to expect to replace them more often if they carry heavy lime. Sediment can also form large masses that stop the tank draining. In that case, the maker says, have a qualified person use a de-liming agent suitable for drinking water: that is what a water heater descaler is for.

Signs a water heater is going bad in a Valley home

These come from A. O. Smith’s manuals:

• Rumbling or percolating sounds: sediment collecting at the bottom of the tank. Flushing is the fix.
• A rotten-egg smell from the hot water: the most common complaint linked to the anode rod.
• Water on the floor: check where it is coming from. The maker says many suspected leakers are not leaking tanks; loose fittings or condensation can be the source. But once the anode rod is used up, the tank starts to corrode and will eventually leak. A. O. Smith states plainly that all water heaters eventually leak, and recommends a drain pan piped to a drain.
• Less hot water than before. See below.

Only 10 minutes of hot water? Causes the maker lists

A. O. Smith’s troubleshooting charts list these causes for too little hot water or slow recovery:

• Thermostat set too low
• Sediment or lime in the tank
• A heater too small for the household’s use
• A cracked, leaking or melted dip tube, or reversed connections (usually found soon after installation)
• On electric models, a burned-out upper element or a faulty thermostat
• A leak on the hot water side of the plumbing

You can check the thermostat setting yourself. For elements, dip tubes, gas controls and wiring, have a qualified person take a look.

How to flush a tank water heater: A. O. Smith’s steps

These steps follow A. O. Smith’s manuals for its gas and electric tank heaters. Your own manual comes first. If you’re not comfortable doing it, the maker says to contact a qualified person, such as a water heater flushing service.

1. Turn off the heat. Gas: turn the gas control to OFF and close the manual gas shut-off valve. Electric: switch off the heater’s circuit breaker.
2. Let it cool. Run a hot tap until the water runs cool, to lower the risk of scalding.
3. Attach a hose to the tank’s drain valve. Run the other end to a drain, outside, or into buckets, and secure it.
4. Drain. Close the cold water supply valve, open the drain valve, and open a hot tap to help the tank empty faster.
5. Flush. If sediment came out, open the cold water supply with the drain still open and let water run until it runs clean.
6. Close up. Close the drain valve and remove the hose.
7. Refill. Open a hot tap, then open the cold supply. Leave the hot tap open until water flows steadily without air (A. O. Smith says three minutes after a constant flow for its gas models).
8. Turn the heat back on only when the tank is full. Relight a gas heater by the label instructions, or switch the breaker back on. Check for leaks.

How often to flush a water heater on Valley water

Advice varies by source, so follow your heater’s manual:

• The Department of Energy says to drain a quart of water every three months to remove sediment.
• A. O. Smith’s gas heater manual recommends draining and flushing every six months.
• Its electric heater guide says to drain and flush after the first six months, then at least yearly, or more often depending on how hard your water is.
• ENERGY STAR’s heat pump water heater guide lists yearly flushing and checking the anode rod.

Anode rod replacement, softeners and Phoenix homes

A. O. Smith says each of its tank heaters has at least one anode rod, a metal rod that corrodes instead of the glass-lined tank. It is a consumable part, not covered by warranty, and hot water, heavy use and water softening all wear it down faster. Never remove it for good: that voids the warranty.

A. O. Smith calls artificially softened water “exceedingly corrosive” and says a softener may shorten the tank’s life. With softened water, its gas manual says to inspect the anode within three years and then yearly. Replace it if most of the rod is thinner than 3/8 inch or about a third of its core wire shows.

The World Health Organization sees the other side: softened water causes less scale and probably means longer life for water heaters. If you are choosing a water softener in Arizona, plan on checking the anode more often, and work out your size.

Tankless vs tank lifespan in Arizona

A tankless heater has no tank to corrode, hence the Department of Energy’s 20-plus years. But its fact sheet says the heat exchanger is likely to scale in mineral-rich water and should be flushed with a descaling solution. See hard water and tankless water heaters.

Repair or replace a Valley water heater?

A. O. Smith’s manuals give replacement steps for heating elements, thermostats, anode rods and drain valve washers, and say lime-encrusted elements are in most cases easier and cheaper to replace than to clean. A leak from the tank itself comes from corrosion, which new parts can’t fix. Have a qualified person confirm where any water is coming from first.

Where these facts come from

• U.S. Department of Energy · Energy Saver guide (2022) and a tankless water heater fact sheet (2009) · lifespans, quarterly draining, tankless scaling
• City of Phoenix Water Services Department · annual water quality report · 2025 · hardness range and scaling in water heaters
• A. O. Smith · residential gas heater manual (2014) and electric heater use and care guide (2017) · sediment, flushing steps and schedule, anode rods, softened water, warning signs, troubleshooting
• ENERGY STAR · heat pump water heater buying guide · 2021 · yearly flushing and anode checks
• World Health Organization · background document on hardness in drinking water · 2011 · softened water and water heater life