About once a year
Flush a standard tank water heater about once a year to clear sediment, or every six months if you have hard water. Inspect the anode rod every one to a few years depending on your water, and replace it once more than six inches of the core wire shows.
A water heater fails in one of two slow, preventable ways: sediment builds up in the bottom of the tank and makes it work harder, or the sacrificial anode rod wears out and the tank itself starts to corrode. Flushing handles the first. Checking the anode rod handles the second. Neither is glamorous, and neither gives you any warning before the day you have no hot water or a leak on the floor.
This one has real safety steps, so read them before you start: the water is scalding and an electric element must never run in an empty tank.
How to do it
- Shut off power at the breaker for an electric unit, or set the gas valve to pilot for a gas unit. Turn off the cold water supply valve.
- Connect a garden hose to the drain valve at the base of the tank and run it to a floor drain or driveway. The water will be scalding, so let the tank cool first if you can.
- Open a hot-water faucet somewhere in the house to let air in, then open the tank's drain valve.
- Let the tank drain, then briefly reopen the cold inlet to stir and flush the remaining sediment until the water runs clear.
- Close the drain valve, remove the hose, and close the hot-water faucet.
- Reopen the cold inlet and let the tank refill fully. When a steady stream flows from that open faucet, it is full.
- To check the anode rod, shut the cold supply again and remove the rod with a socket. Replace it if more than six inches of core wire is exposed.
- Restore power, or return the gas valve from pilot to its normal setting and relight per the label. Once a year, briefly lift the temperature-and-pressure relief valve lever to confirm it flows and reseats.
Common mistakes
- Leaving an electric unit powered while the tank is empty. The element can dry-fire and burn out within minutes.
- Draining scalding water carelessly. Let it cool or route it straight to a drain, never onto skin or plastic.
- Leaving a nearly spent anode rod in place. It depletes unevenly and can fail fast at the end, leaving the tank to corrode.
This is exactly the kind of thing that is easy to know and easy to forget. Adulting can put it on a cadence so it surfaces when it is next due, instead of when something goes wrong. Free to start.
Sources
Questions people ask
- What does sediment actually do?
- It settles at the bottom of the tank and insulates the water from the heat source, so the unit runs longer, costs more, and can overheat and crack a glass-lined tank.
- What about a tankless water heater?
- Tankless units have no tank to flush and no anode rod, but they do need descaling roughly once a year to clear mineral buildup from the heat exchanger, especially on hard water.