The Sacrificial Anode Explained

Modern hot water cylinders are incredibly energy efficient – when you compare their overall efficiency to things like endless hot water systems heated by gas, they stack up very well indeed. The cylinders of today last a lot longer too, with the need for hot water repairs greatly reduced thanks to a small thing that is found in every cylinder – it’s called a sacrificial anode. Here’s why it is so important in the ongoing performance and longevity of your hot water cylinder.

The sacrificial anode prevents the breaking down of the tank and components. That word  “sacrificial” will give you a clue as to why that is. The anode (also widely known as an anti-corrosion rod) is typically made of magnesium, aluminium or zinc. It’s installed on the top of hot water tanks and is similar to the anodes used in various types of vessels like ships, barges, tankers, and is also used around docks and harbours.

Through a process known as electrolysis, the sacrificial anode will corrode in place of the cylinders’ exposed steel. This happens whenever metal needs protection from the water and occurs when two pieces of the submerged metal react to the voltage. During this process, more reactive metals like zinc, magnesium or aluminium will corrode before the less reactive metals like copper and steel. In other words, the anode basically gives up its own well being so the rest of your hot water cylinder can live long and prosper.

As you can appreciate, sacrificial anodes are vital components in hot water cylinders. For all that, many people have no idea they exist. Because of this, and all of the corrosive material they attract, anodes are often neglected and become severely degraded over time. They are no longer able to do their job of looking after the rest of the cylinder – this is when problems can occur and the rest of the hot water system can begin to break down. This is when a cylinder replacement is most often called for as repairs are very difficult to carry out at this stage and could be largely ineffective anyway.

On the other hand, by replacing the sacrificial anode you can easily add years to the life of your hot water cylinder. By contacting us, we can check on the condition of your anode and the cylinder in general and give you our advice on the best way to proceed.


As registered Master Plumbers our work is covered by the Master Plumbers Guarantee for 12 months, giving you peace of mind.