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If you’re like most people, you probably rarely, if ever, flush your water heater. Flushing is one of the most important parts of water heater maintenance and prevents too much sediment from building up inside the tank. If you have a tankless water heater, then flushing isn’t necessary since the unit doesn’t store any water. Let’s take a look at the reasons why flushing your water heater is so important and the steps involved in doing it.


Flushing the tank is important as sediment buildup is the primary reason that most water heaters fail. When water enters the tank and is heated, it causes many of the dissolved minerals in it to solidify into sediment. As the sediment builds up, it can damage the unit’s heating elements. Sediment is also the reason that water heaters often make loud knocking sounds whenever they are heating. This noise results from air bubbling up through the sediment and causing it to hit against the side of the tank.

Like all other major appliances, it is important that you have your water heater professionally maintained at least once a year. During the service call, a plumber will flush out your water heater to remove any sediment sitting inside the bottom of the tank. You can usually flush the tank on your own fairly easily.

However, what you won’t be able to do is fully inspect the unit and all of its components to ensure everything is working properly. Without this, it is likely that your water heater will have a much shorter life span even if you do flush it regularly. Another reason that professional maintenance is so essential is that your water heater’s warranty may depend on it.


Before doing anything else, it is first necessary to turn the water heater off and let it sit for at least a few hours. This ensures that the water in the tank has time to cool so as to prevent scalding when draining it. Whether doing it on your own or hiring a professional, it’s always best to shut the heater off the night before the tank is drained if at all possible.

Gas water heaters should be shut off by turning the control knob to the “Off” position and closing the gas shut-off valve. If you have an electric water heater, it will be on its own dedicated 220- or 240-volt circuit. To shut the unit off, all you need to do is flip the circuit breaker in your main electrical panel that controls the unit.

There should be a shut-off valve at the top of the tank that controls the supply of cold water to the unit. This needs to be closed to prevent the tank from continuing to refill as it drains. The next step is to attach a garden hose to the threaded connection on the drain valve located near the bottom of the tank.

Most homes have a floor drain located within a few feet of the water heater. In this case, the hose is simply run into the drain. If the water heater is located on the ground floor, there may not be a floor drain. In this situation, the hose will be run from the tank through a door so that the water can drain outside.

Once the water inside the tank is sufficiently cool, it is then necessary to turn one or two faucets on to hot and then let them continue to run. If you don’t have any taps open, it usually leads to a vacuum forming inside the tank that will prevent all of the water from draining.

After opening the faucets, you can then open up the drain valve so that the tank begins draining. Depending on how many gallons the tank holds, it can take anywhere from 20 minutes to an hour for it to drain fully. Once all of the water inside the tank has drained, the cold water shut-off valve is reopened.

When opening or closing the drain valve and cold water supply valve, you must be extremely careful to avoid damaging them. Never attempt to force the valves open or closed, or you could break them and cause a serious leak.

This allows more water to flow into the tank so you can continue to flush out any remaining sediment. When flushing, it is important to regularly check and see what the water coming out of the hose looks like. You will need to continue flushing until the water is completely clear and contains no more sediment.

Once the tank has been fully flushed, you can then close the drain valve and disconnect the garden hose. Finally, turn the unit back on and wait for it to reheat. If you have a gas unit, you will also need to relight the pilot light if the unit uses a standing pilot. For automatic pilots or other ignition systems, all you need to do is turn on the gas, and the unit will automatically light the gas burner to start heating.


When attempting to flush a water heater, oftentimes the drain valve will become clogged with sediment and no more water will flow. If this happens, there are several options that can help clear the clog. The first option is to simply close your hot water tap, leave the drain valve open and wait an hour or so to see if it starts draining. Sometimes, the weight of the water is enough to eventually push the sediment out of the valve.

You can also open up multiple hot water taps to help speed up the draining. Once the tank is mostly empty, turn the cold water back on and wait again to see if it begins to drain. This helps as the new water entering the tank can often help loosen the sediment.

If the tank still won’t drain, it is sometimes possible to clear the sediment out the valve with a coat hanger or stiff wire. It is always important to have a bucket under the valve in case it suddenly starts draining.

The last option is to back flush the tank, which is something that you should always have a professional do. Back flushing involves connecting the tank to a hose bib or other water source. This forces cold water back up through the valve to flush any sediment out of it.

Depending on how much sediment is inside the tank, the drain valve may become clogged multiple times during the draining and flushing process. There are also times when the valve may become too clogged to ever drain. The valve can also break or get damaged and prevent it from draining. In either case, you will need to have a plumber replace the drain valve. Luckily, this can be done quite easily even if the tank is still full.

The key here is to make sure all of the taps are closed as this will trap any air inside the water lines. This creates a seal that prevents most of the water from leaking even when the drain valve is removed. There may still be a small leak, but water won’t come rushing out when the old valve is removed and the new one installed.


If you need your water heater flushed, inspected or maintained, you can count on the experts at 3D Air Services, LLC. Our team works on all makes and models of water heaters, and we install, repair and maintain both tankless and traditional units. We also install and work on whole-house generators as well as heating and air conditioning systems. Our team can also help you with duct cleaning and sealing or installing an air filtration system in your home. We have been serving Alabaster and Shelby County for more than 15 years and are here to help with any of your water heater or HVAC needs. For more information or to schedule a service appointment, give us a call today.

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