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The Importance of Backflushing Your Water Heater

Would you like to save money on energy, prolong having to replace your water heater, plus improve its safety? This article and video will show you why it's important to backflush your water heater, how it's done, and how often it's recommended.


Let's start first with how your water heater works and why it's so important to backflush your water heater.

A water heater is a large insulated cylinder that is filled with water. It has a heat source which raises the temperature of the water from about 50 degrees F to about 120 degrees F. The heat source can be a burner that runs on a fuel such as oil, gas or propane; or the heat source can be electricity.

Water comes into the tank through one pipe, and then the heated water leaves the tank through another pipe. Your water heater tank will have a thermostat that controls its temperature, and it will also have a drain faucet at the bottom, and a pressure relief valve at the top.

As your water heater heats up the water in your tank, dissolved minerals that are naturally present in the water are released from being suspended in the solution, and as these minerals precipitate out, they begin to accumulate at the bottom of your tank as what is called 'sediment.' As the sediment layer builds up, it creates two problems:
  1. the layer of sediment acts as insulation, which means that your water heater needs to use more energy to heat up the water in your tank; and

  2. this sediment can cause corrosion in your tank, which can lead to an early failure of your tank.

Regularly backflushing your water heater washes out these sediments from the bottom of your tank, and thereby helps you: save up to 5-10% on your water heating costs; can extend the life of your water heater by up to 5 to 10 years; and help improve the safety of your tank.


So now let's look at how to backflush your water heater. There are 11 steps for doing a complete and thorough backflushing of your water heater:

STEP 1: To get started with backflushing, if you have an electric heater, turn off the power at the circuit breaker, and for gas models turn the thermostat on the unit to the 'pilot' position. It is very important that you do this, otherwise you can risk damaging your water heater or its heating elements.

STEP 2: Then connect a garden hose to the drain valve at the bottom of the tank and put the other end either in a five-gallon bucket, a floor drain, or run the hose outside. If you have a recirculation pump for your hot water system, then turn this off (see types, costs, and reviews of water buckets).

STEP 3: Next, shut off the supply valve for the cold water inlet to the water heater.

STEP 4: Then, open a hot water faucet in a sink closest to your water heater and open another hot water faucet in a sink that is at the highest point in your house. When you do this only a little water will flow out since you have shut off the water supply valve to your hot water heater in STEP 3.

STEP 5: Next, lift the lever on the pressure relief valve at the top of your tank to open this valve. You might want to place a rag or small bowl under the vent pipe to catch any water that might come out.

STEP 6: Then, open the drain valve in your tank and drain one to two gallons from the tank. The water coming out of the garden hose will be scalding hot so be careful that the water doesn't splash anywhere except in the bucket, drain or outside. Also, if your water heater is located near your furnace, be careful not to accidentally touch any hot pipes or surfaces that could burn you. As the water begins to drain out you should notice sediment in the water stream. You will want to continue to let the water flush out until you no longer see any sediment and the water stream is clear. If no water comes out when you open the valve, then sediment is likely clogging it. If this happens, you should close the valve and then contact a professional to clear the valve for you.
STEP 7: Next, to refill the tank, first close the drain valve and remove the garden hose. Check carefully that the valve is not leaking, as sometimes sediment can get stuck in it, which will keep it from closing tightly.

STEP 8: Then close the pressure relief valve at the top of the tank.

STEP 9: And, then open the valve for the cold water inlet to the tank, and you should start to hear the tank filling with water.

STEP 10: Then walk around and check the faucets that you opened in the house. At first only air will be coming out, but after you begin to get a steady stream of water from the faucet, you can then shut the faucet.

STEP 11: And finally, for electric water heaters turn the power back on and for gas models turn its thermostat back to its 'on' position. And if you have a recirculation pump, then turn it back on too. After your water heater has been back on for several hours, you will want to check that no water is leaking from your pressure relief valve, as sometimes opening and closing it can cause it to stick slightly open (helpful accessory: leak detector alarms).

These are the 11 steps for doing a thorough backflushing of your water heater. On the other hand, there is also a 'shortcut' backflushing you can do for your water heater, that involves just doing STEP 6. By opening your unit's drain valve and allowing a few gallons to rapidly drain out, this can help to remove some of the sediments from the bottom of your tank. It is not a thorough as doing all 11 steps, but it is still helpful, and much better than not doing anything at all.


Regarding how often to backflush your water heater, you should backflush your water heater at least once each year. And to maintain the highest efficiency and longest useful life of your water heater, we recommend that you should backflush your water heater 3 to 4 times per year. If when you are backflushing, you don't see much sediment coming out, then you do not need to backflush as many times per year.

You might want to consider having a profession do a full, 11-step backflushing when they are doing the annual inspection and servicing of your HVAC systems, and then doing the 'shortcut' STEP 6 backflushing yourself in between.

A couple of important notes:
  1. If you are backflushing your water heater yourself (even just the 'shortcut' STEP 6 approach), you need to be VERY CAREFUL, as the water can be extremely hot; and

  2. Most service technicians who do your annual inspection and servicing for your HVAC systems will NOT backflush your water heater unless you specifically ask them to do it.



The benefits of backflushing your water heater are significant. Routinely flushing out the sediments from the bottom of your tank will help you save money on energy, extend your water heater's useful life, and will improve its safety. We hope this video has helped you understand why, how and when you should backflush your water heater.

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