Hot water tanks – How long do they last?


Hugh Cairns: Hot water tanks – How long do they last?

My clients always ask how long a hot water tank is expected to last. Since the tank is sealed and there are no mechanical parts to inspect it’s often hard to tell. Perhaps the best way to estimate its life expectancy is simply to determine its in-service age. Depending on the internal quality of parts in a gas water heater, tanks generally reliably last between 8 to12 years, electric water heaters typically last a little longer.

When a water heater is properly maintained, it can last longer. However, hot water heaters can have shortened lives due to poor or dormant maintenance. Tanks that have been drained and flushed of sediment regularly should have increased the life expectancy.

Water heaters typically fail due to rust, corrosion of steel and copper components, or burning hot spots & pinholes in the bottom of the tank due to accumulation of sediment or from hard water. In the case of sediment accumulation, think of your tank as a tea kettle with a layer of sand on the bottom. The accumulation of sediment acts insulating layer, requiring you to keep turning up the burner to heat the water. The burner fatigues faster shortening the life of the burner and tank. This process eventually results in a leaking tank. So, estimating the remaining life of a tank is kind of like a crapshoot. The warrantied life of a tank is a remarkably good way to estimate its reliable life.                                

When it comes to replacement, the way that I look at it is you can have a soft ending or a hard one. The hard ending is when your tank fails and leaves you without hot water until you can get it replaced. The soft ending is the one where you budget for a new tank, research for the one you want and have it installed when it is the most convenient for you. You may also be able to purchase a new tank on sale and save a bit of money. So, is it worth squeezing those last few years out of the tank?                         

One more thing to consider is that some people do not replace their hot water heater until it fails, believing it is fine until that time. In fact, a unit can operate at a decreased efficiency level for several years before it completely fails.

Every water heater has a TPR valve (TPR stands for Temperature Pressure Release) that opens in the event that the tank pressure is too high or the water is too hot. If you ever see water leaking out of the TPR valve you should be concerned. The tank requires immediate attention. A leaking valve indicates that the valve has become defective or the pressure in the tank is exceeding the relief point.

If the cause is a leaky TPR valve, in most cases it can be replaced. As the valves get older they sometimes begin to leak. TPR valves are relatively inexpensive. Usually there is only one problem replacing them, sometimes they’re a bit hard to unscrew.  You may need a long handled wrench with a cheater.  Turn off the gas or electricity and cold water supply to the tank. Drain enough water to get below the level of the valve. Don’t drain a lot of water until you’ve broken the valve loose, so the weight of the water helps keep the heater from moving while you pull on the wrench. Wrap some Teflon tape on the threads of the new valve and when you replace it.