We cannot stress enough the importance of getting your hot water system serviced. Your system contains parts, like anodes, that help keep it running for many years to come if they are serviced regularly.
Last week, one of our plumbers was called to replace the anode in a hot water system. The customer had had it done previously so knew it had to be done.
You should have the anodes replaced every 4 years to protect the tank from the water attacking it. Instead the water attacks the anode and breaks it down. This then settles at the bottom of your tank.
As part of our service, we flush the tank, removing this sediment.
How do anodes work? Anodes are manufactured from a special grade of magnesium and they protect steel by a sacrificial electrochemical action. Magnesium is electro-negative relative to steel. When a magnesium rod is fitted to a steel tank filled with fresh water, a current will constantly flow through the water between the rod and any exposed steel area on the tank wall. The circuit is completed through the tank back to the magnesium rod. This protective current is produced by the magnesium releasing ions, and this results in corrosion in the anodic area. The magnesium (the anode) corrodes instead of the steel tank (the cathode). This principle of electrolytic corrosion control is called cathodic protection. Because cathodic surfaces cannot rust, the steel tank is protected.
What is an anode and why is it so important? Water heaters have anodes in them to protect them against rust.
All mains pressure, storage water heaters, other than those made from stainless steel, are constructed from 2 to 3 mm thick mild steel which has been coated on the inside with vitreous enamel similar to that which is used to rust-proof barbeques. They are never made from glass or fibreglass. Any misunderstanding here stems from the industry term “glass-lined which is commonly used to describe this type of tank.
This enamel coating is subject to extremes of temperature and pressure which causes it to deteriorate over time. Therefore, all glass-lined tanks are also fitted with one or more sacrificial anodes to protect the steel tank against corrosion as the glass lining loses its effectiveness. Even in places like Sydney and Melbourne, where the water quality is quite good, anodes in small water heaters can last for as little as 4 or 5 years before being expended and thus allowing corrosion to commence.
By simply replacing a heater’s anode when required, (the period varies depending on the size and model of the heater) the same protection is provided that keeps ships afloat, underground steel pipelines and tanks corrosion free. – That’s why the heater manufacturer put the anode there in the first place.
How do you know your anodes need replacing? You will either have no hot water (due to the sediment blocking the valves) or your system will be making a bubbling or rumbling sound (we call it kettling).
Having the anodes replaced regularly will extend the life of your system (its also a good chance to get it checked over by a plumber).