Water Heater Failures

Water heater failures and the resulting leaks are a common and recurring problem. Most water heaters have a glass (sprayed on coating) layer over the steel that provides some protection to the inside of the tank. This is also why it is not advisable to drink water from a water heater as some glass particles end up in the water.

However, the main protection comes from the anode. The anode, available at most home improvement and hardware stores, is a rod of sacrificial metal (aluminum or magnesium alloy) that preferentially corrodes, thus protecting the steel. When the anode is gone, so is the protection.

Notice the X-ray of an electric heating element on the right. It should have been horizontal but the leak allowed the water to escape and the element overheated and drooped. In a gas water heater, this could have been much worse.

Tank corrosion will almost always become evident adjacent to a weld. This is because of the greater corrosion vulnerability of the heat-affected zone along the weld, which is normal.

To the untrained eye, the corrosion may look like a weld failure and the direction of corrosion (inside out or vice versa) is not always apparent due to the relatively low pressure and the leakage that often precedes a catastrophic failure.

Since the function of the anode is to corrode, it will eventually be consumed and it should be checked regularly and replaced when the sacrificial metal has been consumed.

The photo on the right shows the heating element control on the side of the water heater.

Water heaters should be maintained annually by flushing and checking of the anode. If a lot of flaky white material comes out of the drain valve, or you have "smelly" (sometimes sulfur smelling) hot water, you need to change the anode. The T&P valve (Temperature and Pressure relief valve) should also be activated at least annually to make sure it is free of corrosion and operates correctly.

However, don't go home and activate the T&P valve lever! If it is older than about 2 years, it probably will not reseal due to compression set of the gasket.

Also, the outlet should never be plugged, as that will prevent the safety device from properly protecting the water heater. While this will not cause an explosion, it could cause a rupture. Steam explosions occur when very little water is in the tank and the water becomes superheated.

For an electric heater, there are usually two heating elements that are installed into the side of the tank, one high and one low. Low dollar units generally contain only one heating element located about a third of the way up the tank. On gas fired water heaters, corrosion failures resulting in leakage can cause problems including fires, steam explosions and others.

The photo on the right shows the top of a typical gas fired water heater with the draft hood removed. The anode is the stainless nut on the top. The large hole in the center is the flue. Note the dielectric connections for both the hot and cold water connections.

I have worked on well over 100 water heater failures and have seen the typical corrosion failure, as described above handled in a myriad of ways by insurance carriers. Some deny the claim due to lack of maintenance. Some pursue the manufacturer. Still others have pursued the installer for failure to leave the manual with the homeowner.

Failures may also be the result of a manufacturing defect, and if a carrier is going to pursue subrogation, they should use an engineer that knows the difference between the various failure modes and how to handle the analysis. Avoid getting into a position of using a generic product inspection firm or individual who will assert a defect claim when the evaluation lacks an accurate explanation of the corrosion process, the protection and/or the failure modes.

Water heater tank after the exterior sheet metal was removed and the insulating foam was removed. Note the split (dark vertical line) in about the middle of tank.	Top of tank from the inside. Note that there are 4 ports. The one on the left is the stainless rod for the anode. The stainless rod is what the sacrificial material is plated onto, this one has no sacrificial material left. The other three, from top, hot outlet, T&P relief valve, cold inlet (downtube).
Close-up of the corrosion around the weld, which is horizontal in this photo. Note the generally vertical fatigue lines. As the steel is oxidized, the material weakens and starts to flex due to thermal and pressure cycling.	A standard T&P relief valve.

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