How often should you flush a water heater?

Flushing the water heater is one of those tasks that does nothing visible, right up until the day it saves you a few hundred dollars and a cold shower. It is easy, cheap, and almost everyone forgets it. Here is how often to do it and why it matters.

The short answer

Flush a tank water heater once a year. If you have hard water, make it twice a year, because minerals build up faster. A tankless water heater should be descaled every year too, or more often on hard water.

That is the rule. The rest of this guide is why, and how.

Why sediment is the enemy

Your water carries dissolved minerals, mostly calcium and magnesium. Inside a tank heater, those minerals settle to the bottom as sediment. Over time that layer:

• Wastes energy, because the burner has to heat through a crust of mineral before it warms the water, which shows up on your bill.
• Shortens the heater’s life, by trapping heat against the steel tank and stressing it.
• Reduces hot water, since sediment takes up space that used to hold water.
• Makes popping or rumbling sounds, the noise of water boiling under the sediment.

Flushing clears that sediment out before it can do the damage. It is the single most valuable thing you can do to make a water heater last.

Tank versus tankless

The two types need different care.

A tank heater is flushed: you drain the water out through the bottom valve, which carries the loose sediment with it. This is the once-a-year job most people mean.

A tankless heater has no tank, so it cannot collect sediment the same way, but minerals still scale up the heat exchanger. It needs descaling, circulating a descaling solution or vinegar through it, on a similar yearly schedule. Many tankless units now warn you when they are due.

How to flush a tank water heater

The basic steps, though always check your model’s manual first:

1. Turn off the heater. For gas, set it to pilot. For electric, switch off the breaker.
2. Shut off the cold water supply to the tank.
3. Connect a garden hose to the drain valve at the bottom and run it to a drain or outside.
4. Open a hot water faucet somewhere in the house to let air in.
5. Open the drain valve and let the tank empty, carrying the sediment with it.
6. Briefly turn the cold supply back on to stir up and rinse out the last sediment.
7. Close the drain, refill the tank fully, then restore power or gas.

If you are not comfortable around gas or electrical connections, this is a quick and inexpensive job for a plumber.

Signs yours is overdue

• Rumbling or popping from the tank.
• Hot water that runs out faster than it used to.
• Rusty or cloudy hot water.
• A higher energy bill with no other explanation.

When to flush versus when to replace

Flushing extends life, but it does not make a heater immortal. Most tank heaters last 8 to 12 years. If yours is past that, leaking, or rusting from the tank itself, flushing will not save it, and you should plan a replacement instead. See when to replace home appliances and systems for the full lifespan picture.

Never forget it again

The reason almost nobody flushes their water heater on schedule is simple: it happens once a year, so there is nothing to remind you. HomeAlmanac puts it on a yearly cadence tied to your home, reminds you when it is due, and logs the date you did it, so you always know when the heater was last serviced and when the next flush is coming.

Ten minutes a year is the trade for years of extra life from a major appliance. Worth setting a reminder.