Flush a tank water heater once a year. Make it about every six months if you have hard water, or if your house goes through a lot of hot water. A tankless unit is a different job: it gets descaled on a schedule instead of drained like a tank.

Rheem, which makes water heaters, says it plainly: for most households, flush the water heater once a year to keep sediment from building up. With hard water, every six months. Heavy hot water use, or sediment you can already see, can mean more often. Tankless systems need periodic descaling rather than a traditional flush.

Home Depot’s how-to guide lands on the same yearly timing: unless the operator’s manual suggests a different frequency, drain and flush the tank once a year. It also says to read that manual first, because the exact steps change a little from one model to the next.

So the short answer is once a year, unless your manual says otherwise. Your manual beats any schedule on the internet, including this one.

What the flush is actually removing

Minerals ride in with the water, settle out, and pile up on the bottom of the tank. A little more every month, and nobody sees it happen.

Rheem describes what that layer does once it gets thick: it sits between the burner or the element and the water, like insulation. The heater runs longer to do the same work, parts wear faster, and the tank does not last as long as it should. Flushing is just draining the grit out before it gets deep.

How often to flush a tank water heater

Once a year is the baseline for most homes.

Move to about every six months if any of these fit your house:

Hard water
A lot of hot water every day: a full house, long showers, laundry most nights
Sediment you can already see coming out of a tap

Flush it now, whatever the date says, if the tank is rumbling or the hot water runs out early. Those are signs the sediment is already deep.

And if your manual gives its own number, use that number instead.

When hard water means every six months

Hard water just means there are more minerals in it. More minerals in means more grit settling in the tank, so a yearly flush leaves too much behind.

You can usually spot it without a test. White crust on the showerhead and the faucets. A film on glasses out of the dishwasher. Scale in the kettle. Soap that never quite lathers. Cheap test strips will give you a number, and many water utilities publish one for the area. If that sounds like your water, put the flush on a six-month schedule and stop thinking about it.

Tankless water heaters get descaled, not flushed

A tankless unit has no tank sitting there collecting grit, so there is nothing to drain in the same way. Rheem says these need periodic descaling instead: a cleaning solution run through the unit to clear mineral buildup.

How often, what solution, and whether your unit needs a service valve kit are all answers in the manufacturer’s instructions for your model. Read those first. It is still a real recurring job, just a different one.

Signs sediment is building up

Rheem lists the early warnings, and they show up before anything breaks:

Rumbling or popping noises from the tank
Rusty or cloudy hot water
Running out of hot water faster than usual
Longer waits for the hot water to come back
An energy bill climbing without anyone using more

One of these means move the flush up. Several of them, on a heater you cannot remember ever flushing, means read the next two sections before you touch a valve.

The safety parts, before anything drains

This is not a full set of steps. The steps for your heater are in its manual, and that is where I would send you. But a few things are true for every tank.

Turn off the power or the gas first. Both Rheem and Home Depot start there. An electric unit gets its power shut off. A gas unit gets the gas handled the way the manual says.
The water coming out is hot enough to burn you. Send it to a floor drain, or outside, or into something you can carry safely.
Do not turn the power back on until the tank is completely full again. An element firing in a dry tank is ruined in minutes.
Follow the manufacturer’s order of operations. Which valve, in which order, and where it sits on your model are things the manual knows and I do not.

When to call a plumber instead

Rheem is specific about when this stops being a homeowner job. Call a licensed plumber if:

The drain valve will not open, or it leaks
There is heavy rust or corrosion around the fittings
The noise keeps up after a flush
The unit is 8 to 12 years old or older
You are not comfortable with the gas or electrical side of it

Add one more: a tank that has never been flushed, and you do not know how old it is. Rheem warns that older or long-neglected tanks can hold hardened sediment that will not come out without proper tools, and that trying anyway can cause leaks or more damage.

Hiring it out is a normal choice, not a failure. If you do, write down who came, the date, and what they told you about the tank. A year from now that note is the only thing that will remember it. Keeping track of home contractors covers what is worth saving.

How to remember the yearly flush

An hour of work, once a year, on a machine in a closet nobody looks at. That is the part that goes wrong, and it is not because people are lazy.

Nothing prompts you. A flushed heater and a neglected one look exactly the same from the doorway. By the time the tank starts popping, it has been filling up for years. In a shared house it is worse: one person does it, nobody else knows, and three years later two people each figure the other one handled it.

Tobi’s maintenance log is built for a job on this kind of clock. The water heater becomes a record of a real thing in your home, with the manual link saved right on it, so nobody goes hunting for the model number again. “Flush water heater” becomes a task on that record that repeats every twelve months, or every six with hard water. Mark it done and the next date moves forward on its own.

A few things that help with this one:

Every completion is saved with the date, who did it, and notes, so “water ran clear after five minutes” or “plumber replaced the drain valve” stays attached to the heater instead of living in someone’s memory.
Nothing is written over, so you can see how the last few flushes went and whether the tank is getting worse.
If a plumber does it, the work can be logged under that contractor instead of a person.
Tobi reminds you the day it is due, and again the next day if it is still not done.

Everyone in the household sees the same record on their own phone, in real time. So the flush shows as due for the whole house, and once someone does it, it is done for everyone. One subscription covers the household and only the owner pays, so the people you live with cost nothing to add. The pricing page has the numbers.

How the flush fits with the rest of your home maintenance

The flush is one of a dozen jobs in a house that come back on their own clocks. The furnace filter. The dryer vent. The gutters. The smoke alarms.

None of them are hard. They just come due quietly, while everyone is busy with something louder. The home maintenance schedule that actually survives real life puts the monthly and yearly ones in one place.

Go find the sticker on your water heater, read the manual, and pick your date. Then write down that you did it, so next year is a reminder instead of a guess.

How often to flush your water heater