What kills water heaters: rust, pressure, neglect, corrosive air

What you'll find on this page: There is a variety of ways for a water heater to die. Some are obvious, while others are insidious.

Neglect

Yep, folks. The most dangerous enemy of water heaters is often the people who buy them, install them and then forget about them. That's you. But it doesn't have to be that way.

This heater was beneath a house and clearly, nobody had checked in on it in a long, long time. Mark your scheduler or calendar so this doesn't become your heater!

Leaks can develop over time and can slowly destroy a heater from the outside. When it starts to look like this, it's a little too late to worry about other measures. But if you ignore a heater past the point it needs maintenance, this can happen inside the tank, too.

A long-neglected water heater that has started to leak from the top

A new sacrificial anode compared with a 7-year-old one

Internal Rust

Sacrificial anodes get used up. If they aren't replaced when they're "down to the wire," the tank starts to rust and eventually, leaks. Even a powered anode won't save a tank then.

It's worth pointing out here that often water softeners speed up anode consumption. Under normal circumstances, if you have a 6-year-warranty water heater, you can wait until the six years are almost up to check your anode. People with softeners should check them once a year or once every two years. Another option for people with softeners is a powered anode. It is a permanent replacement to the sacrificial anode and does not get used up and does not need to be replaced.

Sediment Buildup

Sediment, also known as scale, is created when hard water is heated. It builds up in the bottom of the water heater, where it insulates the bottom of the tank from the protection of the anode, while also causing the bottom to overheat and melt away the protective glass lining.

It's no wonder many people say, "The bottom dropped out of my water heater and it flooded the garage." The bottom probably DID drop out.

Too much sediment can also void warranties in commercial heaters.

Corrosive Fumes

Now this is one that wouldn't occur to a lot of people. But water heaters draw air in for combustion and the quality of that air is important. We're not blaming all this on Clorox -- we just had the bottle handy. It can also be ammonia or acids or anything else near the water heater that qualifies as corrosive.

If the heater draws corrosive air into the burner, then the fumes created will also be corrosive, and corrode the water heater. This can lead to premature tank failure.

Having corrosives and the water heater in a small, closed space concentrates the fumes and makes them worse.

High Water Pressure

This is a hidden killer of water heaters and one a lot of people wouldn't even suspect, much less test for. The water pressure gauge at right is on the drain valve of my own water heater. It shows pressure between 60 and 80 psi.

Anything over 80 psi can damage water heaters, piping and appliances. If you have pressure that high, you need a pressure reducing valve and possibly an expansion tank. The latter will protect against damage from thermal expansion, which can occur when a heater fires up in a closed system to maintain temperature, but when nobody is using hot water.

One giveaway is when the temperature/pressure relief valve starts opening and closing. But don't trust to that; often they stop working with time.

A water pressure gauge on the drain valve of a water heater

Improper Sizing

How hard does your water heater have to work? Does it run all the time? All the water heater manufacturers have sizing programs that will let you punch in number of people, number of bathrooms, number of appliances and get a gallonage and Btu figure, usually along with several models that fit those parameters.

If you buy a heater that is too small for the task it will perform, eventually it will break due to constant expansion and contraction of the tank, even if pressure is within limits and the anode is changed regularly.

Transient Current

Now, this one is REALLY esoteric, but electricity that comes from other sources can also cause jump to the water heater or piping and cause corrosion. One way to prevent it is to connect the incoming and outgoing piping with a length of #6 solid copper wire above the water heater and then running that to the ground bar at the main electric panel.

Leaking Unions and Flex Lines

These fittings need to be tightened after about six months because the rubber washers will shrink and start to leak. That, coupled with neglect, can mean the demise of a heater that rusts from the outside in.

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