How to Flush a Water Heater | Direct Energy Blog

How to Flush a Water Heater

Welcome to the Take Charge of Your Home series from Direct Energy! Hiring a professional to perform household maintenance may offer convenience and peace of mind, but you can do many of these jobs yourself with no experience or special tools. And in the process, you’ll save money, learn about how your home works and gain a sense of accomplishment from a DIY task done well!

Your water heater is one of those appliances that is extremely easy to take for granted. It’s out of sight, out of mind, and can do its job for years on end without any maintenance at all.

That’s a bad idea, of course. Like most appliances, water heaters require periodic maintenance in order to maximize energy efficiency and the lifespan of the unit. A neglected water heater may keep hot water flowing for a few years, but it will gradually cause your utility bills to creep higher and will eventually fail altogether.

The best way to protect your investment is to have your water heater serviced annually by a licensed plumber. A good plumber will conduct a full inspection for rust, leaks and other problems, test the thermostat and valves, replace the anode rod to prevent corrosion and flush the tank. But that last task — flushing the tank — is one you may want to perform yourself as often as every few months, depending on the mineral content of your local water supply. Learning how to flush a water heater on your own can save you a lot of money over time.

How to Flush a Water Heater | Direct Energy Blog

Why Should I Flush My Water Heater?

2 words: hard. water.

What is hard water?

All water has some degree of mineral content. If you live in an area with lots of limestone beneath the ground, the groundwater will pick up calcium and magnesium deposits, resulting in “hard” water. The U.S. Geological Survey provides a map that shows water hardness by region.

What issues can hard water cause?

Hard water causes all sorts of problems: it leaves dishes spotty, makes laundry feel scratchy and can make it hard to rinse away soap in the shower. It also affects water taste in a way many find unpleasant. But while those issues are easy to notice, hard water can wreak hidden havoc inside your hot water heater tank.

Minerals form sediment on the inside walls of the tank and all its internal parts. In electric water heaters, this sediment can coat the heating elements and cause the unit to heat less efficiently. In gas water heaters, sediment on the bottom of the tank can create hot spots that weaken the tank’s structure and can cause leaks. And in both, sediment buildup can clog the drain valve.

In neglected water heaters, this sediment can accumulate and calcify, making it difficult to remove. This can get so bad that the entire unit may need to be replaced. But if you flush your tank regularly, you can prevent sediment from causing problems. Most homeowners should do this every six months or so, but if you have extremely hard water, you may want to do it more often.

Before You Begin a Water Heater Flush

There are two important things to consider before you perform this maintenance. First, if you have a gas water heater, you should find out whether its pilot light must be lit manually. The best source for this information is the original owner’s manual, because pilot lighting procedures vary among models. If you don’t have a manual, check the water heater’s label for a brand name and model number and try to look up the manual online. There may also be pilot lighting instructions printed on a label on the tank.

Second, make sure you have a garden hose capable of reaching from your water heater to a floor drain, bathtub or outside. If your water heater is located in your attic or in a less accessible space, you might need to buy an extra long hose to allow you to drain the tank. While this may add to your water heater flush cost, it’s a small one-time expense compared to the ongoing savings you’ll collect from improved efficiency and extended water heater lifespan.

The process described here applies to conventional tank water heaters, but tankless water heaters are also susceptible to damage from mineral sediment. There is a completely different process to flush tankless water heater equipment, and a pump is required to circulate water through the system. You can pick up a tankless water heater flush kit with detailed instructions at most hardware stores.

How to Flush a Water Heater | Direct Energy Blog

How to Flush Your Water Heater

1. Shut off the power to your water heater at your circuit breaker panel. If you have a gas water heater, you should also shut off the gas supply using the valve on your water heater’s gas line.

2. Cool your water (optional). Some homeowners like to let the water cool before proceeding, especially if they plan to route the drain hose into their yard and are worried about killing grass. To do this, you can either wait a couple of hours for the heated water to cool, or you can run your hot water tap for several minutes to drain it.

3. Shut off the cold water supply valve leading to your water heater.

4. At any sink, turn the hot water on full blast — this will prevent a vacuum effect that could damage your pipes or water heater.

5. Open the pressure relief valve. Locate your water heater pressure relief valve, which is usually a short brass valve assembly near the top of the tank. Position a bucket underneath and open the valve’s trip lever. A small amount of water should drain out. Keep this valve open for now.

6. Route your hose and drain. Attach your drain hose to the drain spigot at the bottom of the tank, then route your hose to a safe draining location. When you’re ready, open the drain spigot — which may require a screwdriver — and allow the entire tank to drain.

7. Flush with clean water. When the tank is empty, reopen the cold water supply valve to flush the tank with clean water. You only need to do this until the water coming from the drain hose is clear and free of sediment, so it can be helpful to have a partner at the other end of the hose to tell you when the tank is clean. If you’re going it alone, collect a glass of water from the drain hose after about a minute of flushing, then shut off the water supply. Wait a few minutes to see if sediment begins settling at the bottom of the glass, and if so, or if the water is tinted, flush some more.

With your tank now clean, it’s time to get your water heater running again. Fully close the drain spigot, remove the hose, close the pressure relief valve and open the water supply — in that order. Go to the sink where you left the hot water running and turn it off as soon as the water is flowing at full pressure. Flip the circuit breaker switch to restore power, and if you have a gas water heater, reopen the gas supply valve and relight the pilot using the process recommended by the manufacturer.

That’s all there is to it! Your tank is now clean and won’t need to be flushed again for weeks or months, depending on how quickly sediment accumulates in your area.

Flushing your water heater is a simple process that can save you big bucks over time. But just in case you run into trouble — a sediment-clogged drain spigot, stuck pressure relief valve, faulty pilot light or some other problem — be ready to reach out to a local plumber for professional backup.

See how your DIY home improvement projects can help your energy efficiency with an electricity plan from Direct Energy! We give you the tips and tools you need to track your usage and see how energy efficient you are.  You could even get free electricity every weekend in select states!

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Josh Crank is a freelance writer and content marketer with a background in legal journalism, travel writing, and marketing for numerous commercial industries. He's found his perfect fit at Direct Energy in writing about home maintenance and repairs, energy efficiency, and smart home technology. Josh lives with his wife, toddler son and endlessly howling beagle-basset hound mix in New Orleans.