Written by Daniel Walker, Walker Company Heating & Air (303) 386-4082
This is a question that we get a lot. To answer this question we first have to understand why water heaters fail in the first place. Sediment is the enemy of all water heaters, whether it be a 40+ gallon or a tank-less unit sediment build up is the number one cause of water heater failure. As sediment builds in the bottom of the water tank or heat exchanger the heating surface in contact with the flame is unable to transfer heat as effectively to the water. This results in longer heat times and more importantly over heating and metal fatigue of the water tank (heat exchanger). Under normal conditions water heats and rises being replaced by cool water. This process continues until the water has reached its temperature setting. When sediment has been allowed to build, temperatures of the heat exchanger must become hotter to heat the sediment and then the water. The higher temperatures eat away at the heat exchanger eventually forming pin holes or an all out failure (major flood).
Where does sediment come from? Sediment, in most cases, is a build up of minerals left behind when water is heated. On well water systems sediment can actually be sand or other particles from the well itself further contributing to the build up in the bottom of your heat exchanger. If you are on a well water system it is very important to have a whole house sediment filter installed to protect your water heater, and appliances from this type of sediment. This can greatly increase the life span of your water heating system. Whether you are on well or city water, sediment filter, or not sediment is going to build up in the bottom of your heat exchanger. Water heater manufacturers recommend flushing the sediment out of your water heating system at minimum once a year (more often if your water is particularly hard). Tank-less water heaters need to be flushed and cleaned by a qualified professional usually once a year. All other water heaters can be flushed with the following steps.
NOTE: If your water heater has been installed more than five years without any maintenance, it may be too late to flush. If the tank will not drain, sediment likely has built and clogged the drain. In this case, it would be a good time to start budgeting for a replacement water heater.
If your water heater has been installed more than five years without any maintenance, it may be too late to flush. If the tank will not drain, sediment likely has built and clogged the drain. In this case, it would be a good time to start budgeting for a replacement water heater.
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Turn the gas off to the water heater. For electric models, turn the power off.
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Turn the cold water supply off to the water heater.
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Hook a hose to the drain valve at the bottom of the water heater and run it to a drain or outside.
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Open the drain valve and drain the water heater about 1/3 of the way.
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With the hose still connected and the drain still open, turn the cold water supply back on and allow the tank to purge under pressure for about ten minuets.
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Close the drain valve and allow the tank to refill with water.
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Open a hot water faucet at the highest location of your home to allow air to purge out of the water tank.
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Turn the gas back on and relight the pilot. For electric models, turn the power back on.
That´s it! You have successfully flushed your water heater. You can write the date on a piece of tape and apply it to the water heater so you will know when the next service interval has arrived.
The next line of defense for your water heating system is called a sacrificial anode. All water heaters, with the exception of tank-less systems, have an anode installed from the factory. A sacrificial anode is a rod made of one of three metals: aluminum, magnesium or zinc. This device has an important role in protecting your water tank from rust. A sacrificial anode works by having a more negative charge than the metal it is protecting. When electrolysis begins, the anode corrodes instead of your steel water tank. Sacrificial anodes work great unless you have very conductive water (it has a very high mineral content). If your water is high in mineral, you likely need to filter it before it enters the water heater. Your anode should be checked once a year during your water-tank flush. The anode is usually about three feet long. If you have inadequate room above your water heater to remove the anode, the water heater will need to be disconnected from the plumbing to remove the anode. Replacement anodes are available sectioned to defeat problems with clearance above the water heater.
How long does a water heater last? Without any maintenance it is hard to say. A good ballpark is seven, to ten years. With regular maintenance, they can last twenty plus years. It is always best to perform maintenance. If you are unable to perform maintenance yourself, hire a knowledgeable contractor to perform the work for you.