How to Drain a Water Heater

how to drain a water heater

And Can I Flush My Water Heater Myself?

Like all home appliances, a hot water tank has an expiration date. Home Depot states that with proper maintenance, a tank-style hot water heater should last 6 to 12 years and tankless versions more than 20 years. Since periodic flushing of a water heater is considered standard maintenance, you really should have it done. You certainly want to extend the life of your hot water tank as long as possible.

Whether you choose to use a plumber or do it yourself is completely up to you.

My gas hot water tank blew out a few months shy of 10 years, foiling my proactive plan to replace it at the 10-year mark. I freely admit I never had the tank drained, even though I know I have hard water. After the mess of hot water spraying everywhere, paying for an emergency plumber to cut off the tank’s water supply (I couldn’t reach the cutoff valve with all the hot water and steam), the inconvenience of no hot water for several days, and paying a second company to install a new tank, now I know better.

I vowed to do a hot water tank flush once a year.

I also freely admit I’m a chicken when it comes to plumbing—even for something as basic as draining a hot water tank. So, I called my plumber. I would watch how he did it, then decide if I wanted to tackle it myself next time.

Just a quick note before we dive in. There are a variety of ways to drain a hot water tank. What I describe is how my plumber did it, which differs a bit from other methods. To read other suggested methods to flush a water tank, check out these articles from HGTV, The Spruce, and Forbes

But first, what makes up the sediment in a water heater?

According to the USDA, there are naturally occurring minerals found in our water supply that plumbers have determined are the main culprits. These include:

  • Calcium
  • Natrium
  • Magnesium
  • Kalium
  • Copper
  • Iron
  • Manganese
  • Zinc
  • Phosphorus

And sometimes, other odd particles come through our water systems and end up in the tank too. The result is a nasty coating that builds up on the bottom and works its way up the sides. It also coats the heater’s anode rod which is supposed to be the first line of defense against the corroding effects of minerals.

water heater anode rod

New and corroded anode rods

Step 1: Prep the area

Fortunately, as my gas hot water heater is in the garage, it was easy to clear things out enough for the plumber to work. And since I knew a water tank is drained through the brass drain valve by way of a garden hose, I had one handy, just in case the plumber needed a longer run.

how to drain a water heater

Some of the key, lower areas on the hot water tank to which the plumber needs access

Some hot water heaters have a knob above the drain valve to open and close it. Mine has a slot that accepts a standard screwdriver.

how to drain a water heater

Note the nice, wide slot on top of the drain valve. The blue pipe is where water from the tank's pressure relief valve would flow out should it happen to let loose. It’s not relevant to the water tank flush process.

If I didn’t have a way to drain to the outside, the alternative would have been using one or more buckets, making for a slower, potentially sloppier process.

Time for the plumber.

Step 2: Connect the garden hose

After the plumber arrived, the first thing he did was attach the hose, making sure it was tightly fastened. He didn’t want hot water running anywhere except out the end of the hose and onto the concrete driveway.

how to drain a water heater

Step 3: Turn the temperature dial to low (or off if electric), and on top of the tank, turn the cold-water inlet feed off and disconnect the hot water outlet

Thanks to an internal safety sensor, my gas water tank won’t fire up when it senses the water level is low. I didn’t know this, but my plumber did. So, there was no need to turn off the gas supply or set it to Pilot. All he had to do was turn it to the Low position.

how to drain a water heater

The dial easily turned from its normal B position to Low.

The picture below shows the cold-water inlet hose on the right with its long shutoff handle pushed up to the off position. On the left you can see the hot-water outlet at the tank has been disconnected. Alternatively, he could have undone the connection at cold-water inlet. Either way works. Doing this at the top of the tank allows air in to help it drain faster.

How to drain a water heater

Here are the two key areas that need to be accessed at the top of the tank. Note the water cutoff lever is in the off position and the supply line on the hot water outlet has been disconnected.

Think of a can into which you’ve just poked a triangular hole, using an old-fashioned church key type opener. When you tilt the can, it takes time for anything to pour out. But once you punch a second hole, the contents pour out faster and more smoothly. The same principle is at work with the hot water tank.

how to drain a hot water tank

Step 4: Open the drain valve and then watch the water flow!

My 40-gallon tank took about a half hour to drain. At first, the water ran clear.

how to drain a hot water tank

Can you spot any sediment? Definitely hard to tell.

Then, sediment finally started to appear. But there wasn’t much, and it was hard to spot against the concrete.

how to drain a water heater

Aha! I finally spotted some! It’s the bigger white particles.

Then, when the water flow rate really slowed down, it was time to go to Step 5. There was no need to run the tank completely dry.

Step 5: On top of the tank, reconnect the hot water outlet then turn the cold-water supply line back on, leaving the garden hose connected and the drain port still open

Now the water tank flush begins in earnest. As the new water vigorously mixes with what’s left at the bottom and sides of the tank, the sediment gets stirred up and really starts coming out.

It’s easier to spot, too.

how to drain a water heater

The sediment looked like rock salt or grains of white rice.

When it started to collect in low spots like the one below, I was surprised at the amount.

how to drain a water heater

Wow! Who knew?

I found many little catchments on my driveway and in the street gutter. I was completely taken aback by how much came out of my tank. And my hot water heater was just 10 months old!

I realized 2 things. My water was harder than I thought. And a flush probably needs to be done twice a year.

Since it’s the mixing action of the incoming water hitting the bottom and sides of the near empty tank that shakes loose the sediment, as the tank filles up, there is less and less scouring. And any loosened sediment that remains becomes more dispersed and less concentrated.

After 5 minutes or so, there was less sediment coming out. The main event was clearly over. I suppose one could repeat the draining and flushing one more time if the sediment discharge was really bad, but my plumber was satisfied with the results.

Step 6: Close the drain port, disconnect the garden hose, and reset the temperature dial

The plumber returned the tank to its operating parameters. He then had me turn on the hot water tap in my tub. This was in case any sediment somehow got pushed out into my home’s hot water pipes. He explained the tub has a larger diameter water inlet hose which enables any particles to pass on through and into the tub without causing a clog. It also helped get rid of any air bubbles that might have formed in the hot water line since that usually happens when water has been turned off. Five minutes later, he instructed I turn the tub’s faucet off. All was well and the plumber left.

It then took another 30 minutes or so for the tank’s water to heat back up.

The draining only took a tad over an hour from when the plumber arrived to when he left. But that short window of time certainly left a lasting impression on me—I absolutely, positively must drain and flush my hot water tank on a regular basis.

The importance of flushing the tank

While the tank was draining, my plumber dropped a little knowledge bomb on me:

Three-quarters of an inch of sediment in the bottom of a tank makes a hot water heater 40% less efficient. And tanks generally are about 89% efficient to begin with.

So, not only does draining a hot water tank on a regular basis help extend its lifespan, but it also keeps it running at peak efficiency so you’re not wasting energy dollars.

And if you’ve noticed your hot water has a rusty color, is creating more limescale on the faucets than normal, or the tank itself is making odd sounds, flush it right away. However, if your hot water has a foul smell, there could be bacteria in your tank. In that case, Angi recommends boosting the thermostat to 140°F for 8 hours to kill the microbes, then flushing the tank.

How often should I flush my water heater?

Experts suggest a water heater flush at least once a year. In my case, given that I have hard water and how much was flushed out, twice a year might be best.

If you own a water softening system that uses salt, you still need to flush the tank. In fact, soft water can actually shorten the life of a tank and require a yearly replacement of the anode rod inside.

How to Drain a Water Heater: Can I Flush My Water Heater Myself?

So, after watching my plumber and noting the steps, I can see myself doing this—sort of. My main worry would be my ability to disconnect and reconnect the hot water outlet on top of the tank and not break something or strip the threads. Or somehow jamming/breaking the long cold water inlet lever while moving it up and down. Break either of those and I’d have to call the plumber anyway.

But like any DIY project, it all depends on your comfort level. If you feel confident or the tank is just a year or two old and the connections haven’t had a chance to corrode, go for it. But have the plumber’s number pulled up on your phone just in case things go wrong.

For the record, my plumber encourages homeowners to flush the hot water tank themselves. His feelings aren’t hurt in the least when basic things like this are handled as DIY project. The only tools required for my gas hot water tank were a slot screwdriver, adjustable wrench for the tank’s top connectors, and a garden hose.

Other hot water tank maintenance tips include inspecting and replacing the inner anode rod every 3 years and testing the pressure relief valve. You may choose to let a plumber do the former and tackle the latter yourself.

Here's another hot water heater maintenance tip. Replace those braided stainless steel connector hoses every 5 years.

And when it’s time, be sure to check out the water heater supply lines from Certified Appliance Accessories. Our sturdy water heater connectors come in both 1.5 ft. and 2 ft. lengths and can be used for both cold water inlet and hot water outflow.

Enjoy your hot water…and give your water tank the TLC it so richly deserves.

Disclaimer: This article is for informational and educational purposes only. Certified Appliance Accessories is not liable or responsible for any damages resulting from or related to your use of this information.