How to Drain a Water Heater

A leaking faucet on a domestic water heater with pipe wrench
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Project Overview
  • Working Time: 1 - 2 hrs
  • Total Time: 1 - 2 hrs
  • Skill Level: Beginner
  • Estimated Cost: $0

Most water heater maintenance manuals suggest that you drain a water heater at intervals ranging from six to 12 months. The reason this is recommended is to help remove any sediment or buildup that collects on the bottom of the water heater tank due to minerals and other particles in the water. This buildup will cause the water heater to work harder to heat the water, using more energy and costing more money to run.

Before You Begin

Before getting started, make sure you know where your home's main water shutoff valve is located. While you won't necessarily need it during this process, it's always a good idea when working with any kind of plumbing fixtures in your home to be acquainted with this valve in case something goes wrong and you need to stop all water flowing through your pipes.

Safety Considerations

This process involves working with water that can be extremely hot. You might want to turn off your hot water heater several hours before you begin in order to let the water in the tank cool off. If you're not able to do that, then use heavy-duty rubber work gloves to protect your hands from any splashes and use safety glasses to keep your eyes safe from hot water droplets.

What You'll Need

Equipment / Tools

  • Adjustable wrench
  • Garden hose
  • Flat-head screwdriver
  • Bucket

Materials

  • Drain valve (if necessary)
  • Threaded hose cap (if necessary)

Instructions

  1. Perform a Quick Flush

    Before you shut off the water, connect a garden hose to the drain valve and try and flush the water heater tank a bit while the water pressure is on. To do this, open the drain valve for a few seconds and then close it again. The pressure will blow out any sediment stuck in the valve and help the tank drain faster. If quite a bit of sediment comes out, you can repeat this a couple of times.

    Be sure that you've run your garden hose to either an exterior location or into your bucket to catch the water and sediment that will be released.

  2. Turn Off the Water Heater

    Shut off the gas to your water heater, or shut off the power if it is an electric heater. Now shut off the water, using either the valve in the cold-water pipe above the water heater or the main water supply valve to the house. Make sure the pressure is off by testing the hot water faucets in the house, turning them on, and checking for water. Water may gush out at first, but should quickly slow to a trickle if the water has been shut off properly. Be sure to leave a hot water tap open in the sink nearest to your hot water heater to alleviate pressure in the system.

  3. Open the Drain Valve

    With your garden hose attached, open up the drain valve. You can usually do this by hand, but you might need to use your flat-head screwdriver here.

    Once the valve is open, water will begin to gush out of the drain so again, be sure your hose either leads outside or into your bucket. As the bucket fills, turn off the drain valve so that you can dump it. Repeat the process as much as you need to empty the tank.

  4. Flush the Tank With Water

    Once the tank is fully drained, you can flush it with a few gallons at a time by turning the water on for few seconds and then letting it drain out again. When the outflow runs clear, you'll know that you've removed the sediment and you can move on to the next step.

  5. Refill the Water Heater

    Shut off the drain valve and disconnect the garden hose. Be sure all but one of the hot water taps in your home are closed (the one in the bathtub closest to the water heater is best).

    Now you can turn the water back on to the water heater. After doing so, monitor the tap you left open and, once you are getting nothing but water out of the fixture, turn it off.

  6. Relight the Water Heater

    Relight the water heater pilot, or turn the power back on if it is an electric heater. Within an hour or so, you should have hot water.

  7. Check the Drain Valve

    See if your water heater drain closed completely by looking for leaks at the spout. If it did not close completely, you can put a threaded hose cap over the hose thread of the outlet to stop the leak. Or, you can replace ​the valve completely.