What is Silica?

Silica also known as silicon dioxide, is a compound made up of silicon and oxygen.

Silica is very common in the earth’s crust and is only slightly soluble in water. Things like sand, quartz, and granite. Many animals and plants also use it to build their skeletal structures.

As New Zealand is a volcanic country, we have higher levels of dissolved reactive silica than other parts of the world.

In many cases it is mistaken for hardness, as it can cause scale which looks very similar, but is extremely difficult to remove.

How does Silica get into my water?

Silica dissolves in as it passes rocks and minerals which contain it. It is far more common in groundwater sources than others.

What does Silica do?

Silica is harmless to humans, and in fact, may even be beneficial. Supplements containing silica are available.

However it is a bit less kind to plumbing, particularly where water is heated or allowed to evaporate, a white scale will be left that can only be cleaned by abrasion.

This can cause blocking of pipes, damage to hot water cylinders and other water-using appliances as well as water spotting on shower glass and tapware.

How can I remove silica?

Silica can be removed by reverse osmosis or by strong base anion resin.

However, there are a number of difficulties with silica removal. It needs to be done for the whole supply, rather than at the tap as the pipework is where most of the damage happens.

Strong anion base resin is rarely used in smaller commercial or domestic applications as it is regenerated with caustic soda, which is a dangerous chemical to handle and may be subject to disposal requirements.

Reverse osmosis is more commonly used, but more in commercial applications than domestic due to the cost and space of the plant required.

Another option more commonly used in domestic applications is dilution by rainwater.