The worst possible time to find out your water heater has died is when you are in the shower with a head full of shampoo. Water heaters are often taken for granted and pushed well beyond their intended life spans. Knowing when a water heater is about to give up the ghost can not only prevent icy showers, but also save money at the same time.
Conventional tank-style electric and gas-fired water heaters are cylindrical appliances that warm and store a specified amount of water -- typically 40 to 80 gallons. Their expected service life is 10 and 15 years, according to the U.S. Department of Energy. Of course, this life span is dependent upon the water source, maintenance and several other factors. "Tankless" water heaters are different from tank-style heaters in that do not store water, but instead use a series of pipes surrounded by heating elements. Often more expensive than tank-style heaters, tankless water heaters can last up to 30 years.
During the average life span of a water heater, the minerals that have dissolved into the water source collect on the inside of the tank and can slowly corrode the tank over time. Calcium and lime, in particular, react when heated and bind to the inside of the tank. Hard water, which has a high lime or calcium content, can reduce the life span of a water heater by two or more years. Additionally, some sources of water, such as springs and wells, can pull up sediment and deposit sand and mud inside the water heater, reducing its effectiveness even more quickly that minerals. A water heater that uses hard water or well water should be drained, or flushed, about once a year to help extend the life of the tank.
Many tank-style water heaters include an anode rod made of aluminum, magnesium or a zinc alloy. The rod extends down into the tank cavity and attracts corrosive elements in the water, thus preventing those same elements from corroding the tank. If you have hard water, it may be advisable to replace your tank's anode rod about every 5 years. Replacement is a relatively simple process involving partially draining the tank, unscrewing the anode rod and pulling it out of the tank. If overhead space is limited, you may have to cut the rod as you extract it; for replacement, there are collapsible rods available that are made up of loosely linked sections. Consult the tank's owners manual and/or manufacturer to learn about anode rod replacement. Replacing the rod may void the warranty on some models.
The size of a water heater may have an effect on its life expectancy as well. If a water heater is too small for the household and is constantly heating large volumes of water, this may damage the glass lining of the water heater, wear out the heating elements faster or cause electrical problems. Water heaters that are too small may need to be replaced earlier than they should. Conversely, a water heater that is too large can waste energy by keeping the large volume of water heated at all times, even when there's no demand for it. While this can be wasteful and expensive, it does not have an effect on the life span of the appliance.
No matter what kind of water heater used, regular maintenance will increase its life span. A certified heating and plumbing specialist can detect potential problems, recommend filtration systems (if necessary) and take other measures to prevent a premature breakdown of the water heater. The manufacturer of your water heater may have specific requirements for routine maintenance, so consult the owner's manual before calling a plumber. Regular maintenance can extend the life of your water heater by up to five years.