Last Updated December 2025

Draining or flushing your water heater removes mineral sediment that can build up and slow heating capacity, raise energy bills and lead to corrosion, leaks and failure. Signs it may be time to drain your water heater include rust-colored water, reduced hot-water volume or popping sounds from the tank. Most manufacturers, as well as the Environmental Protection Agency, recommend annual servicing, including inspection of key components along with draining and flushing. (Read more seasonal home maintenance tips.)

So, how do you flush a water heater? First, it’s important to note that draining a water heater can be dangerous if not done properly – risks include scalding from hot water, electric shock, gas leaks or flooding. Consider hiring a licensed plumber to handle the job or consult a professional for advice about your specific model of water heater. To get an idea of what it takes to drain the tank yourself, keep reading.

Necessary tools

• A garden hose long enough to reach from the water heater to a floor drain or outside drainage area. 
• Work gloves and eye protection for safety. 
• A flat-head screwdriver or sillcock (utility key) depending upon tank type and drain valve design. 
• A bucket to catch drips, a wet/dry vac or rags and towels for cleanup. 
• The owner’s manual, for model-specific details about hose connection points, valves and restarting the heater. 

Water heater preparation

Turn off the gas or electricity to water heater. Reference the owner’s manual for precise information and images.

Turn off the cold water supply. This prevents the tank from refilling while it's draining. Typically, this valve is blue, or marked “C”, and is located on top of the tank on the water line.

Allow the hot water in the tank to fully cool. This may take up to 24 hours. Hot water under pressure can lead to burns.

Connect hose to drain valve. Attach hose to the threaded valve, typically located near the bottom of the water heater. (Not to be confused with the temperature and pressure (T&P) relief valve, which is not a drain; it is a safety backstop that opens if temperature or pressure gets too high.)

Route the hose to a floor drain or outdoors so that the discharge end is below the level of the water heater and gravity can help the flow. If the hose can’t run downhill or the flow won’t start, water can be drained bucket by bucket from the drain valve.

Drain the water heater

Open a nearby hot water faucet to let air into the plumbing system and help the tank drain more smoothly. Then, open the tank’s drain valve (using a flat-head screwdriver or sillcock key if your model uses one) and allow water to flow out until it stops. Until you refill the tank, leave power supply controls turned off.

How long does it typically take to drain a hot water heater?

Standard tank (40-60 gallons): 15 to 30 minutes
Large tank (80+ gallons): Up to 1 hour

If there’s no drain valve: Some older or specialty models may lack a standard threaded drain connection. Check the owner’s manual for an alternate method.

If the flow slows to a trickle or stops: Sediment in the tank may be blocking the drain valve. If this happens, try opening the cold water supply for a few seconds to help push sediment out. If flow does not resume, the owner’s manual may recommend service by a licensed plumber.

Flush the tank

With the drain valve still open, briefly turn on the cold water supply to flush out remaining sediment. Repeat this short rinse until the water runs clear. Close the drain valve and disconnect the hose.

Refill and restart

Open the cold water supply and let the tank fill. Depending upon your tank size, water pressure and your pipe size, this can take 10 to 30 minutes. The tank and lines have refilled when an open hot water tap runs steadily with no sputtering.

Close the hot water tap but leave the cold water supply open (the drain valve remains closed). The gas/electricity to the heater should remain off until the tank is full.

For gas water heaters, reopen the valve in the gas line and follow the manual’s instructions to restart or relight the water heater. For an electric water heater, flip on the circuit breaker and follow restarting instructions. As a last step, check the tank and all valves for leaks.

How to drain a tankless water heater

Tankless water heaters follow a different cleaning process called descaling or flushing. A solution of water and vinegar or citric acid is run through the machine via its two ports to dislodge and dissolve mineral deposits. Your owner’s manual may provide a guide for how to do it and what cleaning solution to use.

Does homeowners insurance cover water damage?

Homeowners insurance may cover sudden and accidental water damage. But water damage that occurs because of problems that happen slowly over time – such as an old hot water heater that has not been properly maintained flooding your basement – is generally considered a maintenance issue, and maintenance issues typically are not covered by home insurance.

• Regular maintenance like draining your water heater can help prevent the kind of leaks that can lead to water damage.  
  
• A leak detection system can help you catch problems before they cause water damage.  
  
• Keep notes and receipts from routine maintenance in case you need to file a water damage claim. 

See policy for exact details. In the event of a conflict, policy language prevails.  

The information contained in this page is provided for general informational purposes only. The information is provided by Farmers^®and while we endeavor to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to this article or the information, products, services or related graphics, if any, contained in this article for any purpose. The information is not meant as professional or expert advice, and any reliance you place on such information is therefore strictly at your own risk. 

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