Water Heater Maintenance: The Routine That Doubles Tank Life

Flush your water heater once a year, check the anode rod annually (every six months once the tank passes eight years old), test the temperature-pressure relief valve during the same visit, and keep the thermostat at 120°F. That's the whole routine. It costs almost nothing in parts, takes roughly an hour a year, and it's the difference between a tank that rusts through at year six and one that quietly works past year twelve.

Why this matters more than most maintenance: a water heater doesn't fail politely. A tank that corrodes through dumps its entire contents wherever it sits, then keeps refilling until someone shuts the water off. Replacement runs $800 to $2,500 installed, and the water damage from a sudden failure can cost far more than the heater. Everything below pushes that day back, or at least makes sure it arrives on your schedule instead of at 2 a.m.

How often should you flush a water heater?

Once a year for most homes. Hard water and well water build sediment faster, but annual is the baseline that keeps most tanks healthy.

Early fall is the sweet spot: September or October, before incoming groundwater turns cold and run times get long. A tank carrying a layer of sediment has to heat right through it all winter.

Sediment is the quiet killer here. Minerals settle out of the water and collect at the bottom of the tank, where they cut heating efficiency by 20 to 40 percent while accelerating corrosion from the inside. Skip flushing for a few years and you've traded a 12-year tank for a 6-to-8-year one. You'll often hear the damage before you see it: a popping or rumbling sound as water boils up through the sediment.

There's a sneakier reason to flush annually: a drain valve that's never opened tends to seize or clog with the very sediment it's supposed to release, and once it does, flushing may not be possible at all.

How to flush the tank

Nothing here is exotic, but you're working with scalding water, so go step by step. Budget 30 to 45 minutes, or pay a plumber $100 to $200 for the full annual service.

1. Turn the gas control to "pilot", or flip the breaker off for electric. Electric elements burn out almost immediately if they run dry.
2. Attach a garden hose to the drain valve near the bottom of the tank and run it to a floor drain or outside.
3. Open the valve and let 2 to 3 gallons run out. It'll come out cloudy or gritty at first. Keep going until it runs clear.
4. Close the valve, remove the hose, and restore power or gas.

You don't need to empty the tank. A partial flush pulls the loose sediment off the bottom, does most of the work, and is far gentler on an older drain valve than a full drain-down.

While you're standing there, look the unit over. Rust streaks around fittings, dampness at the base, corrosion on the supply connections: any of these is your early warning, and early warnings are the entire point of the visit.

The anode rod: the $20 part that doubles tank life

Every steel tank ships with a sacrificial anode rod, a magnesium or aluminum rod threaded into the top that corrodes on purpose so the tank walls don't. Once the rod is spent, corrosion moves on to the tank itself, and there's no undoing that.

Check it once a year. Unthread it (a breaker bar helps, plus a second person to steady the tank), pull it out, and look. If more than half is eaten away, or you see bare steel core wire, replace it. A new rod costs $20 to $40 and the swap takes about 30 minutes; a plumber will handle it for $100 to $250 if the old one won't budge.

Once a tank passes eight years old, check every six months; that's when rods are typically near the end. A functioning anode rod can roughly double a tank's life, which makes this about the best return in home maintenance. There's a fuller breakdown of that math in our post on what preventive maintenance actually saves.

Test the TPR valve

The temperature-pressure relief valve is the last device between an overheating tank and a dangerous pressure failure. Testing takes a couple of minutes; do it during the annual flush visit.

Put a bucket under the discharge pipe, lift the test lever briefly, and let it snap back. You should get a burst of hot water that stops cleanly when you release. Two failure modes: nothing comes out (stuck valve, can't relieve pressure), or it keeps dripping afterward (worn seal). Either way, replace it. Cheap part, not optional.

If there's an expansion tank on the cold supply line, knuckle-test it annually too: hollow on top, solid on the bottom. A waterlogged one sends a pressure spike to the heater every time it fires.

Set the temperature to 120°F

120°F (49°C) is the number to remember. Higher wastes energy and puts scalding water at every tap; noticeably lower lets bacteria grow in the tank. Gas heaters have a dial on the gas valve; electric models hide the thermostat behind an access panel (kill the breaker first). If the dial shows "warm/hot/very hot" instead of degrees, run a tap for a minute and check it with a kitchen thermometer.

Tankless water heaters: descale once a year

No tank doesn't mean no maintenance. Tankless units trade sediment for scale, mineral deposits that coat the heat exchanger and choke off heat transfer. Two jobs keep them honest:

• Descale annually. Circulate white vinegar through the unit with a pump kit ($20 to $40, reusable for years) for 45 to 60 minutes, or pay $150 to $300 for a pro service. On well water, do it every six months. Skip it and you'll see falling hot-water output, then error codes, then a unit that lasts 10 years instead of 20.
• Rinse the inlet filter every six months. A small screen on the cold-water inlet catches debris. Pull it, rinse it, reinstall. Ten minutes, free, and it prevents the mysterious "why is my hot water weak" service call.

Gas heaters: check the venting

If your heater burns gas, add two quick annual checks the same day as the flush. First, make sure the unit has breathing room: no boxes stacked around it, no sealed closet without vents. Starved combustion produces carbon monoxide. Second, eyeball the vent pipe. It should slope upward toward the chimney with every joint secure and no soot marks around the draft hood. Soot means exhaust has been spilling back into the house: call a pro today, not later.

Know when to stop maintaining and start planning

Standard tank heaters last 8 to 12 years; heat pump models stretch to 12 to 15. The manufacture date is encoded in the serial number on the label (each brand does it differently; search the brand plus "serial number date" to decode yours). Inside the last couple of years, start collecting replacement quotes. A planned swap costs $800 to $2,500 and happens on a Tuesday you chose. An unplanned one comes with a flooded floor and emergency rates.

Common questions

How often should I flush my water heater?

Once a year, ideally in early fall before cold groundwater raises the workload. Drain 2 to 3 gallons until the water runs clear; a full drain isn't necessary.

How much does water heater maintenance cost?

Nearly nothing if you DIY: the flush and TPR test cost $0 to $5, and an anode rod runs $20 to $40 every few years. A professional annual service is $100 to $200, and a pro anode swap is $100 to $250. For how those numbers stack up against the rest of the house, see what home maintenance costs.

How long should a water heater last?

A maintained tank heater typically reaches 10 to 12 years; a neglected one often fails at 6 to 8. Heat pump water heaters last 12 to 15 years, and a well-descaled tankless unit can reach 20.

Is it too late to flush an old tank that's never been flushed?

Carefully. On a tank that's 10+ years old with heavy buildup, a flush occasionally dislodges sediment that was plugging a weak spot. Do a gentle partial flush, watch for leaks afterward, and put your energy into a replacement plan.

What temperature should a water heater be set to?

120°F. It balances scald safety, energy use, and bacteria control. Check actual tap temperature with a thermometer if your dial doesn't show degrees.

All of this fits in one fall afternoon, which is exactly the problem: it's easy to do once and forget for three years. SeasonKeep builds the schedule for your specific heater (tank, tankless, gas, or electric), times it to your climate, and emails you before each task is due. The free plan takes about three minutes to set up.