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How to Flush a 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

How to Flush a 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.

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.

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.

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.

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.)

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.

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

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

Comments from DIY Community Members

Share what's on your mind and see what other DIYers are thinking about.

1 - 8 of 8 comments
Show per page: 20   All
aoz

September 07, 9:50 AM [GMT -5]

QUESTINO
I have a gas hot water heater.
do I really need to DRAIN this periodicaly, OR can I just turn off the heat, let it get to WARM, leave the water pressure on, and run out about 10 gallons of water?
I just did this, and no real sediment came out anyway, but is ther a reason to ave to dump the whole tank?
thanks
Nick

August 23, 9:58 AM [GMT -5]

I have two water heaters setup in series. Is is necessary to do both, or is one more important than the other?

AAB

May 07, 1:42 PM [GMT -5]

One thing to always check on your hot water heater is if the pipes are connected correctly. I have fixed over 3000 water heaters in a twenty-five year period and at least two or three times a year, I find a water heater that was installed backwards.
The cold water should come in on the right, as you face the controls. If connected backwards, the cold water will come in at the top (left side) and the hot water will have to be pushed through the sediment and up the dip tube.
Most often, the customer complains of restricted water flow on the hot water side.

If you flush a water twice a year it works great, most people never bother until they have a problem, in which case, a shop vac is the only way to clean out a water heater.

September 08, 7:39 PM [GMT -5]

I have had my electric hot water heater for 19 years. Every six months I change the upper and lower rods because of the large amount of calcium in our water. The rods cost around $20 for the both but pay for themselves with-in a few months. I used to vacuum the bottom out by connecting a flexible clear hose to my wet vac and it worked well for many years. Then I found a pvc angled tube made especially to vacuum out the calcium at a local hardware store (not the big guys). I works fantastic and takes less time. Flushing the system never gets all the sediment out and that left over material is what causes the rust to start and then goes your tank. I do like the idea of adding vinegar for those little areas. For energy efficient I always hear of flushing the system but never changing the rods. The rods do build up with calcium causing them to work harder and longer (more energy usage). I do see the big difference in my electric bill every time I change them.

November 20, 5:27 PM [GMT -5]

If you dump a couple gallons of white vinegar into the inlet or outlet of the tank and let it soak in the bottom of the tank of a while it will eat most of the calcium up, or atleast make it easy to flush out with water.

October 06, 1:52 PM [GMT -5]

lefty18jcsOctober 06, 2010

Has anyone tried to loosen the sediment by shooting compressed air through the drain valve? Can this be done without too much danger?

I don't think that is a good idea. You take the chance of forcing some of the sediment into the pipes and causing another problem.

If you FLUSH your tank on a yearly basis (like most manufactors recommend) you shouldn't have a lot of sediment in there.

October 06, 1:40 PM [GMT -5]

One comment only. Instead of taking the handle off you can get a hose thread cap. some types of ball valves the handle is used to seal the bushing in the top; take it off and they will leak

October 06, 1:26 PM [GMT -5]

Has anyone tried to loosen the sediment by shooting compressed air through the drain valve? Can this be done without too much danger?

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