Upgrading Sacrificial Anodes in Water Heating Systems

Blog | October 9th, 2018

Going on that name, sacrificial anodes “give themselves up” over time. The material forfeits its atomic structure, and it does so by design so that a water heating tank gains an essential corrosion resistance feature. If that material base, the anode rod, is a temporary fitting, then it’ll need to be replaced at some point. Here’s what happens when this system-beneficent rod nears the end of its functional existence.

Rod Failure Clues 

Don’t worry about having a sacrificial anode inspected every few months. As the system manual probably points out, this rust avoiding component is built to last. Some materials will easily operate for six years, whereas others are designed to offer up their easily corrodible alloy bases over the course of 10 years. Anyway, when that lengthy period of time does eventually conclude, the old anti-corrosion rod will begin to fall apart. It’ll be so metal-fatigued, so chewed up that it’ll no longer be capable of offering itself up as an alternative corrosion source.

Alternative Material Effects 

Turning first to aluminium, this lightweight element tends to corrode faster than zinc or magnesium, but this effect can terminate in an effect known as “rod passivation.” The makeup of the water forces an aluminium oxide coating to form around the rod, and it stops functioning. Alternatively, the aluminium alloy breaks down prematurely, and little flakes of the corroded metal choke the system filters. Passive films also form around magnesium-based rods. Clearly, then, different sacrificial anode types can either “go to sleep” or decompose faster, depending on the conditions of the hot water. Remember, heat is a rust accelerant here, one that obviously can’t be avoided. Either the soft, mineral-loaded water must be treated, or a more suitable sacrificial anode must be installed as a system upgrade.

Once sacrificial rods bite the dust, water heating vessels start to corrode. Check for passivation, for signs of poor material breakdown. The rod will look like new if it’s not doing its job. Check also for premature material decomposition. Next, upgrade the anode, replace it with a more appropriate alloy type or a fitting that’s ready for 10 more years of rust protecting duty. Before locating the rod, the system needs to be turned off, the water drained, and the vessel made safe. If the entry port is located on the side of the heating tank, then the replacement procedure shouldn’t be hindered. Top-mounted fittings may necessitate some light construction work, which means the tech might have to cut a hole in the ceiling. Alternatively, many rigid rods have flexible counterparts.

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