How to Flush a Water Heater

Sediment can accumulate inside a tank-style water heater over time.

Flushing the tank removes accumulated sediment and can help maintain proper operation and heat-transfer efficiency. The exact maintenance schedule depends on the water heater, water quality, and manufacturer's instructions.

Some manufacturer guidance recommends flushing every six months, while other systems may specify a different interval. Always follow the instructions for your specific water heater.

Because a water heater contains hot water, pressurized plumbing, electricity or gas, this task can involve serious burn, electrical, gas, and water-damage hazards.

If you are uncomfortable performing the procedure or cannot safely follow your manufacturer's instructions, have a qualified professional perform it.

Why Flush a Water Heater?

Water entering a storage tank can contain minerals and sediment.

Over time, this material can settle at the bottom of the tank.

Sediment buildup can:

• Reduce heat-transfer efficiency
• Cause popping or rumbling noises
• Affect water-heating performance
• Contribute to premature equipment problems

The Department of Energy notes that sediment can reduce heat-transfer efficiency and recommends routine maintenance according to equipment requirements.

How Often Should a Water Heater Be Flushed?

There is no single interval that applies to every water heater.

Check your owner's manual first.

Some manufacturer instructions recommend draining and flushing a tank every six months.

Factors that can affect the schedule include:

• Local water quality
• Mineral content
• Type and age of the water heater
• Manufacturer recommendations
• Amount of hot water used

Before You Start

Read the water heater manufacturer's instructions before beginning.

You may need:

• Garden hose rated for the application
• Suitable drain location
• Bucket if appropriate
• Gloves
• Closed-toe shoes

You should also know whether your water heater is:

• Electric
• Natural gas
• Propane

The shutdown procedure differs between models and fuel types.

Important Safety Warning

Water inside a water heater can be hot enough to cause severe burns.

Do not disconnect or manipulate gas components unless you are qualified to do so.

Do not work on electrical connections unless you are qualified.

Never drain a tank while its heating elements are energized if the manufacturer's instructions require the heater to be powered down. Electric heating elements can be damaged if energized without being properly immersed in water.

If you cannot safely identify the correct shutdown procedure, stop and contact a qualified professional.

How to Flush a Tank Water Heater

The following is a general overview. Your manufacturer's instructions take priority.

1. Turn off the heat source

For an electric water heater, turn off the appropriate circuit breaker.

For a gas water heater, follow the manufacturer's instructions for shutting down or placing the heater in the appropriate safe mode.

Do not guess if you're unsure.

2. Allow the water to cool

Hot water can cause serious burns.

Allow sufficient time for the tank water to cool, following the manufacturer's recommendations.

You can also open a nearby hot-water faucet to help relieve pressure and allow hot water to cool through the system.

3. Close the cold-water supply

Locate the cold-water inlet valve supplying the tank and close it according to the manufacturer's instructions.

4. Connect a garden hose

Attach a suitable hose to the water heater's drain valve.

Place the other end somewhere that can safely handle the hot water and sediment.

Never direct the discharge where it could damage the home's foundation, flooring, landscaping, or other property.

5. Open a hot-water faucet

Open a nearby hot-water faucet.

This helps the tank drain and allows air to enter the system.

6. Open the drain valve

Open the water heater's drain valve and allow the tank to drain.

The initial water may contain sediment.

7. Flush the tank

Once the tank has drained according to the manufacturer's procedure, briefly open the cold-water supply as directed to flush remaining sediment from the tank.

Continue until the discharged water is reasonably clear.

Some systems and manufacturers provide specific flushing procedures, so follow the instructions for your particular model.

8. Close the drain valve

Once flushing is complete, close the drain valve securely.

Check the connection for leaks.

9. Refill the tank

Open the cold-water supply.

Keep a nearby hot-water faucet open until water flows steadily without air.

This helps confirm that the tank is filling properly.

10. Restore the heat source

Do not turn an electric water heater back on until the tank is completely full.

An electric heating element can be damaged if energized while not fully submerged.

For gas systems, follow the manufacturer's instructions for restoring operation.

11. Check for leaks

Inspect the drain valve, hose connection, and nearby plumbing.

If you see a leak that you cannot safely correct, shut down the system as appropriate and contact a qualified professional.

How Do You Know If the Tank Needs Attention?

Possible signs of sediment buildup or water-heater problems include:

• Rumbling or popping noises
• Longer heating times
• Inconsistent hot-water performance
• Reduced hot-water capacity
• Rust-colored water
• Leaks around the tank
• Repeated pressure-relief valve discharge

These symptoms can have multiple causes, so flushing the tank isn't necessarily the correct solution for every problem.

When Should You Call a Professional?

Have a qualified professional inspect the water heater if:

• The tank is leaking
• You smell gas
• You see damaged gas connections
• The pressure-relief valve is leaking or discharging
• The water heater has electrical problems
• The drain valve is stuck
• You cannot safely determine how to shut the heater down
• The water heater is very old or heavily corroded
• Flushing does not resolve the problem

If you smell gas, leave the area and follow appropriate gas-emergency procedures rather than attempting to repair the appliance yourself.

Tank vs. Tankless Water Heaters

This guide is primarily for tank-style water heaters.

Tankless water heaters have different maintenance requirements, including possible descaling procedures.

Do not apply the tank-flushing procedure to a tankless unit unless the manufacturer specifically instructs you to do so.

Track Water Heater Maintenance with AruHome

Water heaters are easy to forget because they're usually hidden in a basement, garage, utility room, or closet.

With AruHome, you can record the water heater as a home asset, keep its model and purchase information, schedule recurring maintenance, and maintain a history of completed work.

That makes it easier to keep track of maintenance as the years go by.

Quick Checklist

• Check the manufacturer's instructions
• Identify whether the heater is gas or electric
• Shut down the heat source correctly
• Allow hot water to cool
• Connect a suitable drain hose
• Drain and flush according to the manufacturer's procedure
• Refill the tank completely
• Restore the heat source only when safe
• Check for leaks
• Record the maintenance date