How to Flush Your Water Heater

Do you want to save on heating and maintenance bills? Flushing your water heater might be just the thing.

Do you find your water heater is not quite as efficient as it used to be? Maybe the water isn’t getting as hot or flowing as well as it should. It could be sediment has built up in the base of your water heater, preventing it from functioning well.

You might notice particles in your shower head or in the aerator (filter) on a faucet, looking a bit like sand. Or maybe your water heating is “talking” to you.

Learning how to flush a water heater can remove the small beach that’s forming inside it and quieten things down. It will also save on bills and prolong the heater’s life.

Let’s find out how to tell if you have sediment, and how to get rid of it if you do.

Is There Sediment in My Water Heater?

If you have never flushed your water heater the chances are there’s sediment build up in the bottom of it. Most manufacturers recommend flushing the heater about every six months (1). Here are a couple of telltale signs it might need a washout:

  • Sand-like deposits: When water is heated, calcium and magnesium in the water solidifies and forms a white or tan colored deposit (2). This builds up at the bottom of your water heater and might come through the pipes to your faucet.
  • Noises: Is your water heater telling you there’s something wrong and it needs some TLC? A rumbling noise might be heard as water heats and expands through the sediment. Alternately, you might hear a popping noise as bubbles form and break through this build up. Sizzling, cracking, and hissing from a buried heating element are also possible.
  • Water flow: You might notice that your water doesn’t flow quite as well as it did or that it’s not as hot. Again this is down to a build of sediment blocking its flow and hindering the heating element’s function.

Time to find out how to rectify this issue.

How to Flush a Water Heater

In order to do this, you’ll need to know where your power source is: the fuse box for an electric heater and the gas supply tap for a gas one. You’ll also need a garden hose and a bucket.

1. Turning Off the Power

Gas Water Heater

For a gas water heater, some recommend turning the thermostat to “pilot” while others recommend turning off the gas supply to the boiler.

To turn to pilot:
  1. Locate the water heater thermostat. This is usually on the side of the appliance.
  2. You should see three options on, pilot, and off.
  3. Turn the dial to pilot.
To turn off the gas supply:
  1. Locate the thermostat and turn the dial to off.
  2. Locate the gas pipe to the thermostat and find the lever that turns the gas on and off.
  3. This is generally parallel with the pipe when it’s on and at a 90-degree angle to it when off.
  4. Turn the gas supply off.

Electric Water Heater

For an electric water heater, you will need to locate the fuse box or circuit breaker box. It’s usually a grey box with a hinged door and either has switches or fuses (glass topped shapes or small cylinders with metal ends) inside. It might be in your garage, basement or on a wall on the outside of your home.

To Turn Off the Power Supply From a Circuit Breaker Box
  1. Within the box, there are small on and off switches. These each break the circuit for a branch of the power in your home. If you know which one your water heater is on, then turn that individual switch off.
  2. If you don’t know which individual switch breaks the power for the circuit your water heater is on, then look for a switch labeled “Main.” This is generally a larger switch located above or at the side of the individual circuit breakers.
  3. Turn this switch off. Be aware this will cut the power to the whole house.
To Turn Off the Power Supply from a Fuse Box
  1. If you have fuses as opposed to breaker switches, you’ll need to locate the fuse that powers your water heater.
  2. Unscrew this fuse if you know which one it is.
  3. If you’re not sure then above or at the side of the fuses you should see a box with a lever or handle.
  4. Pull this handle or lever to the indicated “off” position. Again this will cut power to the whole house.

2. Turning Off the Water Supply

Once the power to your water heater has been turned off, you then need to turn off the water supply. The valve that allows you to do this is usually found on the cold water inlet pipe located at the top of the water heater.

There are two types of valve you might come across: a ball valve or a gate valve.

The ball valve will have a lever that you turn through 90 degrees to stop the cold water supply.

A gate valve has a handle or knob that you turn until it stops.

3. Flushing the System

Now that your power and water are turned off you can begin flushing your water heater (3). To avoid accidents from hot water it’s a good idea to turn the heat down the night before.

It’s now time to flush the system. To do this:

  1. Open a hot water faucet in a sink or tub in your home. This stops a vacuum being created which can trap water.
  2. Locate the drain valve or drain cock, normally found at the base of your water heater.
  3. Attach your garden hose to the drain cock or valve. If you don’t have a hose you can always use a drain pan to catch the water, but be careful if it’s hot. Run the end of your hose to a drain or out onto your driveway. If your water heater is in your basement with no drainage available you might need a portable water pump.
  4. If you’re draining hot water then make sure your hoses and buckets are good quality and won’t soften or get too hot. Also, cover the hose connection and drain cock with a rag or towel to prevent water spraying should there be a pressure leak.
  5. Open the drain cock to allow the water to flow from the heater.
  6. Fill a test bucket with water during the draining process and allow it to stand for a few minutes. If you see sediment in the bottom then continue flushing. You want to ideally flush the heater until the water runs clear.
  7. If the tank is empty but you still think there could be sediment in it, then turn the cold water back on. Allow the tank to partially fill and then drain again. You might need to do this a few times until little or no sediment is coming out.
  8. Keep draining until the water runs clear with no sediment.

Things to Consider

There are a few things you need to think about when draining the water heater.

  • You might want to open the pressure relief valve. There’ll be a pipe coming from this valve so make sure you put a bucket underneath it to catch the water. If no water flows when you open this valve, it could be faulty and need replacing.
  • If you let the heater cool overnight you could use the exuded water to wash down the yard or water your plants. Remember it will have sediment in it so don’t use it on delicate plants and definitely don’t use it to wash your car. This is a great way to save on some water while flushing your heater.
  • Always proceed with caution if the water is hot.
  • The drain cock on your heater might be old or could be made from plastic. Be careful not to force it and break it. This would mean calling out a professional and costly repair.

4. Refilling and Turning Water Heater Back On

Now it’s time to get your system working again to supply you with hot water. Start by closing the drain cock and removing your garden hose. If you opened the pressure release valve then close it again.

Turn off the faucet that you opened at the beginning of this process.

Now turn on your water supply and let the water heater fill again. Once it’s full you can open the pressure release valve slowly to let any excess air escape. Close it again once the air is out.

You should then open a hot water faucet again and let any trapped air work its way out. Once the water is flowing freely turn it off again. Remember that it’ll be cold water coming out of the faucet at this stage.

Your water heater is now full and the air has been bled out of the system, so it’s time to restore the power. Either turn on the electric at the fuse or breaker box or restore the gas supply.

If you turned the gas off you’ll need to relight the pilot light and turn the dial on the tank to “on.” If you just turned the dial to pilot, then turn it back on.

After about 20 minutes you should have hot water flowing again from your faucet. If so you have successfully flushed your water heater.

My Water Heater is Old, Will Flushing It Still Work?

The life expectancy of a water heater is on average between 10 and 13 years (4). An issue you might come across with an older water heater is valves that won’t open. If ever you’re in doubt then it’s a good idea to call in a professional.

How Can I Prolong My Water Heater’s Life?

Each manufacturer’s recommendations can differ with respect to maintenance. However, there are a few basic things you can do to keep your hot water supply flowing.

These include flushing the water heater on a regular basis, every three to six months. The pressure release valve and anode rod should also be checked every six months. That said, it’s likely the anode rod will only need changing every three to four years (5).

The pressure release valve is a built-in safety feature that opens and releases pressure if it builds up too much in the heater. When this isn’t working properly the tank can over-pressurize and explode.

We mentioned checking it as part of the flushing process, but here’s how you can do it separately.

  1. Turn off the power to your water heater or turn your gas switch to pilot mode.
  2. Close off the cold water supply to the water heater.
  3. Place a bucket under the hose from the pressure release valve.
  4. Open the trip lever on the valve.
  5. You should see some water and vapor or hear a slight rush of air.
  6. If you don’t then the valve might be faulty and need replacing.

Safety First

Bear in mind that with any home maintenance, safety must come first. If you don’t feel confident enough to carry out maintenance like flushing a water heater yourself then call a professional.

When doing it yourself wear goggles, gloves, and protective clothing. This is especially the case if you don’t let the water cool before draining. Hot water and steam can scald and cause injury.

Flushing Away

Knowing how to flush a water heater can help prolong its life and save on bills by keeping it working efficiently. It’s a maintenance task you should do every six to 12 months and should only take about 30 minutes to complete.

Now you know the steps to follow you can flush your heater and keep the hot water flowing. We hope you enjoyed our guide and found it informative and useful. Please leave us a comment with your thoughts and tips, and don’t forget to share.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.

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