- The valve on the side of the water heater (temperature and pressure relief valve) is dripping water. Is the valve damaged or is there another problem?
- When hot water is drawn from the hot tap it appears to be milky. After a few minutes it clears. What causes this?
- Noise is emanating from the hot water system or pipe work. What is causing this?
- What is the function of an "Anode"?
- I have noticed a puddle of water around the water heater soon after the heater comes on. Is the water heater leaking?
Question:
What is the function of an "Anode"?
Answer:
Sacrificial Anodes
The storage cylinder used in a Rheem manufactured storage water heater is made of mild steel for strength. This cylinder has a continuous coating of vitreous enamel on its internal surface. The function of vitreous enamel lining is to separate the stored water from the mild steel cylinder. This vitreous enamel lining protects the mild steel cylinder against corrosive action by the potable water.
A sacrificial anode is incorporated in the cylinder design for added protection. The anode will extend the service life of the cylinder using cathodic protection.
Cathodic Protection
When two dissimilar metals are connected together and are both in contact via an electrolytic solution, a weak electric current is formed. This weak current produces a cathodic/anodic reaction between the two metals. Therefore, one metal will corrode in order to protect the second metal. The atoms of the less stable metal form a protective coating over the more stable metal.
In the instance of a Rheem water heater, the two dissimilar metals are the anode and the mild steel cylinder. These two metals are connected at the anode fitting at the top of the cylinder. The electrolytic solution is the potable water in the cylinder. The vitreous enamel lining separates the water from the mild steel cylinder, preventing the electrolytic circuit from being complete.
However, if any minute areas of steel become exposed, protection is given by the sacrificial anode. The anode provides protection by forming a protective coating over the exposed areas of mild steel, extending the life of the cylinder.
The rate of protection depends on water quality, level of total dissolved solids (TDS) and water temperature. The most suitable type of anode material is determined by the water quality.
Anode Material
Rheem has three types of anode. The material, its colour code and range of usage is:
| Anode Colour Code |
Material |
Total Dissolved Solid (TDS) content |
| Green Magnesium |
(high potential) |
0-40 mg/L |
| Black Magnesium |
(standard) |
40-600 mg/L |
| Blue |
Aluminium |
600-2500 mg/L |
|
The colour code is the colour of the anode top, applied by Rheem for easy identification. The black anode is fitted as standard into a Rheem water heater.
By using the correct colour coded anode, Rheem water heaters can be used in areas where the total dissolved solids (TDS) content of the water is up to 2500mg/L. In areas where the TDS exceeds 600mg/L it is possible the black anode, which is the standard anode fitted to the heater, may be excessively active. To alleviate this, the black anode should be replaced with one colour coded blue. Where the TDS of the water is less than 40mg/L, such as when the water has been deionised or is from an alpine supply, a high potential anode, colour coded green, should be used. The changing of anodes must be carried out by a plumber or authorised service person.
Anode Inspection
The anode(s) in the Rheem water heater will slowly dissipate whilst protecting the cylinder. The life of the water heater cylinder may be extended by arranging for an authorised person to inspect the anode(s) and replacing if required.
The suggested time after installation when the anode should be inspected is:
| Rheem domestic Rheemglas models |
8 years |
| Rheem domestic Optima models |
10 Years |
| Rheem Heavy Duty models |
7 years |
|
For softened water supplies or in areas of bad water quality, it is recommended the anode be inspected three years earlier than shown. Remember, headroom of one water heater length should be left above the water heater to allow inspection and replacement of the anode if required.
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