How to Flush a Water Heater

Double the life of your water heater

Have you flushed your water heater lately? This boring but important chore should be done at least once a year to remove sediment that accumulates on the bottom of the tank. That's especially true if you live in a hard-water area. The task is easy to blow off because it's out of sight—but skipping it is costing you a lot. Sediment buildup reduces the heating efficiency of your water heater.

By the DIY experts of The Family Handyman Magazine

All about sediment

One sign of excessive sediment buildup is a popping or rumbling sound coming from your water heater. That's the sound of steam bubbles percolating up through the muck. On a gas water heater, the sediment creates hot spots that can damage the tank and cause premature failure. On an electric water heater, sediment buildup can cause the lower heating element to fail. So flushing offers a payback in lower energy bills and extended heater life.

However, if you've never flushed your water heater, or haven't done it in years, you could be in for a nasty surprise. As soon as you open the drain valve, the sediment will likely clog it and prevent you from closing the valve all the way after it's drained. Then you'll have sediment buildup and a leaking water heater. We'll show you the best way to drain the sediment out of even the most neglected heater and save a $200 service call. You'll need about $40 in plumbing parts from a home center, a garden hose, a wet vacuum, pliers and a pipe wrench.

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Buy the parts

Not only will an old drain clog up, but you won't be able to suck debris through its small opening. The key is to build a new drain valve with a 3/4-in. full-port brass ball valve with threaded ends, a 3-in. x 3/4-in. galvanized nipple, and a 3/4-in. MIP x G.H. garden hose adapter (one choice is the BrassCraft/Plumbshop No. HU22-12-12TP).

Then build a shop vacuum adapter. If your shop vacuum has a 2-1/2-in. hose, buy a converter to reduce it to 1-1/4-in. (the Shop Vac No. 9068500 is one option). Then assemble a vacuum hose-to-plumbing adapter with a 1-1/4-in. x 1-1/2-in. female PVC trap adapter, a 3/4-in. MIP x 1/2-in. barb fitting, a second 3/4-in. x 3-in. nipple and a 24-in. piece of 1/2-in. I.D. vinyl tubing.

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Start the draining process

Shut off the gas or electricity to the water heater and open a hot water faucet and let it run full blast for about 10 minutes to reduce the water temperature in the tank. Then shut off the cold water valve at the top of the tank and attach a garden hose to the existing drain valve and route it to a floor drain. (Use a kitchen colander to catch the sediment so it doesn't clog the floor drain.) Then open a hot water faucet on an upper floor and the water heater drain valve. Let the tank drain until sediment clogs the valve and reduces the flow. Then close the upstairs hot water faucet and water heater drain valve.

Next, you'll remove the clogged drain valve and swap in the new full-port valve. But first, remove the blow-off tube and the temperature pressure release (TPR) valve and apply suction to the tank so you won't get soaked when you yank the old drain valve.

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Replace the old drain valve with a full-port brass ball valve

Unfortunately, most water heaters come with crummy drain valves. And once you open them to drain the sediment, the debris clogs the valve, keeping it from sealing. But you can replace the crummy factory drain valve with a full-port ball valve.

While applying suction through the TPR port with a shop vacuum, unscrew and remove the valve by turning the plastic nut behind the knob. If the valve breaks, don't panic. Saw the broken portion with a hacksaw blade until you hit metal threads. Then use a hammer and screwdriver to chip out the pieces.

CAUTION

Remove the ball valve handle after you flush the water heater, especially if the water heater is located where people could walk by it and accidentally bump the handle. The valve could open and release scalding water, causing serious burns. (Twist-tie the handle to the valve so you don't lose it.)

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Finish by removing the remaining sediment

Remove the vacuum hose from the TPR port and flush the tank. Most of the sediment will flush out through the full-port valve. To remove the rest, open the cold water valve at the top of the tank in short bursts to blast it toward the drain. If you still can't get the last bit out, try vacuuming it using the 1/2-inch vinyl tubing and barbed fitting.

When you're done, close the ball valve and leave it in place. But remove the lever handle to prevent accidental opening. Then reinstall the TPR valve and blow-off tube. Refill the water heater and turn on the gas or electricity, and you'll be back in hot water without all the noise.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • 4-in-1 screwdriver
  • Adjustable wrench
  • Bucket
  • Hacksaw
  • Hammer
  • Knee pads
  • Plumbers tape
  • Rags
  • Shop vacuum
  • Slip joint pliers

You'll also need a garden hose.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • Dielectric nipple
  • 1-1/4-in. x 1-1/2-in. female PVC trap adapter
  • 3/4-in. MIP x 1/2-in. barb fitting
  • 3/4-in. x 3-in. nipple
  • 24-in. piece of 1/2-in. I.D. vinyl tubing
  • Brass elbow
  • Dielectric nipple
  • 2" brass nipple
  • Brass ball valve
  • Garden hose adapter
  • Shop vacuum hose adapter