What’s the Reason for Corrosion on Water Heater Connections?

Whether in an office building or home setting, the water heater may be the most underappreciated part of a property. When anyone turns the knob on their shower or faucet, they probably don't give much thought about all the processes that are going on to convert cold water into something that's lukewarm or piping hot.

In reality, the collection of components that comprise a water heater must work collaboratively to generate the appropriate temperature, from the drain valve to the shutoff valve to the sacrificial anode rod and more. With the average home water heater accounting for between 15% and 25% of the property's overall energy consumption, according to statistics from the Environmental Protection Agency, a considerable amount of resources are devoted to this process.

More often than not, water heaters work flawlessly, largely due to advancements in plumbing technology and the durability of residential and commercial heating systems. But when cold water stays cold — or water pressure is unusually low — corrosion may be to blame.

Understanding why this corrosion occurs — and knowing what to look for when it does — can help you address this plumbing predicament.

What could cause corrosion in a water heater?
As mentioned, a water heater is made up of a host of components. While the location of these parts can differ from one model to the next, each usually contains things like a sacrificial anode rod (made out of magnesium or aluminum), which sits within the tank itself, and the shutoff valve, which is separate from the unit and hangs from above.

Pipe connections — for the hot and cold water inlet pipes — are also located above the water heater. When these fittings are made out of steel, they run the risk of corroding due to the combined presence of oxygen and water. Of course, water is constantly flowing through the respective fittings. Over time — typically years — the point where the tank and the fittings meet will decompose in the form of galvanic corrosion.

Galvanic corrosion is among the most common types of corrosion and occurs when two dissimilar metals are fused together or merge at a particular point. For instance, if the fittings that connect the pipes to the water heater are copper and the pipes are steel, galvanic corrosion may result. Usually, there is plastic tubing within the steel pipe, which is designed to shield the metal from coming into contact with water, but this plastic may not be present at the point of connection. As a result, galvanic corrosion can lead to leaking by dissolving the steel pipe threading within the copper fitting itself.

This isn't the only way a water heater may feel the effects of corrosion, however. It could also derive from issues affecting the sacrificial anode rod. The sacrificial anode rod is inside the unit. Crafted from aluminum or magnesium, more active metals than steel, the anode rod sacrifices itself by absorbing the electrochemical response that occurs when water and metal meet, thus shielding the steel from corrosion. But when the protective metal whittles away completely, it exposes the tank to the caustic effects of corrosion.

What can happen if water heater corrosion isn't fixed?
The problem with galvanic corrosion is it's progressive; it only gets worse the longer the issue goes unchecked. And depending on where the leaking is located, water pressure can not only dramatically diminish — affecting fixtures and appliances like the faucets, showers, dishwashers and washing machines — but the pipe joints can burst, causing damage to the home or the plumbing infrastructure itself.

How can you tell if water pipes are affected by corrosion?
Since water heaters are usually located in basements or boiler rooms, they're out of sight and out of mind. Thus, it's the water pressure — or lack thereof — that serves as the first sign of a maintenance problem due to leaking that's happening at the source.

"It's important to have your water heater serviced on a regular basis, ideally once a year."

This is why it's important to have your water heater serviced on a regular basis, ideally once a year. A professional will be able to examine all the components of your water heater by running various diagnostic tests and actively look for signs of leaking. They're also trained to identify corrosion and can make the appropriate modifications so it stops.

Another tipoff to corrosion is your water's appearance or taste. For example, if when pouring a glass of water the liquid is cloudy or contains metal flakes, corrosion is almost certainly to blame. The same is true if the water is clear but the taste is off, this too is a tell-tale sign that something is amiss and it's related to corrosion.

How do you treat corrosion when it affects the water heater?
The single most important element to treating corrosion is identification. If a plumber notices slight rusting on a valve, they may be able to swap out the offending materials so the issue is treated before galvanic corrosion manifests itself.

However, once water has a metallic taste or is discolored, there's no turning back. The water heater will need to be replaced entirely.

"PEX is rustproof, making it immune to corrosion."

Fortunately, fewer and fewer plumbing systems use copper pipes, given that they're so vulnerable to corrosion. Polyethylene cross-linked pipe — also known as PEX — is rustproof, making it immune to corrosion. PEX, polyvinyl chloride (PVC) and acrylonitrile-butadiene-styrene (ABS) are other pipe materials that are preferable for residential and commercial plumbing systems.

However, if you still have copper pipes, ensure that the sacrificial node remains intact and flush with the tank. You can do this by attaching a garden hose to the drain spout and placing the open end of the hose in your drain. Pushing clean water through the tank will carry debris through the hose and out the drain.

Otherwise, consider getting touch with corrosion testing professionals like Auto Technology. We can help you determine the best course of action, which may involve corrosion testing.