How to flush your water heater before winter.

To flush a tank water heater, turn off the gas or power, close the cold water supply, connect a garden hose to the drain valve, open a hot water faucet, and drain the tank until the water runs clear. Then close the valve, refill with the hot faucet open until it runs steady, and turn the heat back on. Once a year keeps sediment from shortening the tank's life, and early fall is a good time to do it.

September is the last easy month for it. If you're on city water in Novi or Farmington Hills, your water comes from the Great Lakes Water Authority's intakes on Lake Huron and the Detroit River, and it comes in colder as fall turns to winter, so your water heater has more work to do every day. Well water around Milford holds a steadier temperature, but it carries more of the minerals that turn into sediment in the first place. Either way, a clean tank heads into winter in better shape.

Before you start

You'll need a garden hose long enough to reach a floor drain or the outside, and a bucket to catch the first bit. The water in the tank is hot enough to scald, so either turn the heat off a few hours ahead and let it cool, or be careful where the hose ends up.

Look at the tank's age first. If it's past 10 or 12 years and has never been flushed, think twice. Old drain valves, especially plastic ones, can crack or refuse to seal once they're opened, and a heavy sediment layer can clog the valve partway through. On a tank that old, it's often better to have us look at it, and our lifespan guide explains why.

Step by step

1. Turn off the heat. On a gas unit, turn the control dial to pilot or vacation. On an electric unit, switch off the breaker.
2. Close the cold water supply. It's the valve on the pipe coming into the top of the tank.
3. Hook up the hose. Screw it onto the drain valve near the bottom of the tank and run the other end to a floor drain or outside, somewhere lower than the valve.
4. Open a hot water faucet upstairs or at a nearby sink. This lets air into the tank so it drains instead of holding water in.
5. Open the drain valve and let the tank empty. Most open by hand, and some need a flathead screwdriver.
6. Stir up the rest. With the drain still open, turn the cold water supply back on for a minute or so. It churns the sediment on the bottom and pushes it out the hose. Close the supply, let it drain, and repeat until the water coming out runs clear.
7. Close the drain valve and take off the hose.
8. Refill. Open the cold supply all the way and leave the hot faucet running until the water flows steadily with no sputtering. That means the tank is full and the air is out.
9. Turn the heat back on. Set a gas unit's dial back to its normal temperature. On an electric unit, only flip the breaker back on once the tank is completely full. An element that powers up without water around it burns out almost immediately.
10. Check the drain valve over the next day for drips.

What you'll see

The first water out is usually cloudy, with grit that looks like sand or small white flakes. On hard well water there can be a lot of it, which is exactly why flushing matters more there, as we explain in our hard water guide. If the flow slows to a trickle while the tank still has water in it, sediment is clogging the valve. Close it, turn the heat back on once the tank is full, and give us a call rather than forcing it.

When not to do it yourself

• You smell gas at any point. Leave the house and call your gas company or 911 from outside.
• The tank is old and has never been flushed. The valve and the tank may not take being disturbed well.
• You have a tankless unit. Tankless heaters get descaled, not flushed, which is a different process with a pump and a cleaning solution. We cover it in tankless vs tank in Michigan.

The rest of the fall check

While you're down there, find the temperature and pressure relief valve on the side or top of the tank. A.O. Smith recommends testing it once a year: lift the lever briefly, some hot water should come out of the discharge pipe, and it should stop when you let go. If it doesn't open, or it keeps dripping afterward, the valve needs replacing. Every few years, the anode rod inside the tank should be checked too, which is a job for a plumber. It's the part that corrodes so your tank doesn't.

If the flush turns up something you don't like, our water heater page covers the repairs and replacements we do in Milford, Novi, and Farmington Hills.

Quick answers

How often should I flush my water heater?

Once a year is what water heater makers like A.O. Smith recommend. On hard well water, which is common around Milford and Highland, it matters even more, because sediment builds up faster.

Can flushing an old water heater cause leaks?

It can. On a tank that's 10 or 12 years old and has never been flushed, the drain valve may not seal again once it's opened, and heavy sediment can clog it. On a tank that old, it's often better to have a plumber look at it first.

Do I need to flush a tankless water heater?

Tankless units don't get flushed the way a tank does. They get descaled, which runs a cleaning solution through the heat exchanger with a small pump. On hard water, that should happen about once a year.

Countryside Plumbing is a licensed master plumber serving Milford, Novi, Farmington Hills, and southeast Michigan since 1979. Water heater repair and replacement is what we're known for, and we leave your house clean. Free quotes at 248-705-7543.