Plumbosolvency

All drinking water is plumbosolvent, which means it can dissolve very small amounts of metals if they come into contact with them.

It is advisable to flush 500ml of water from your drinking-water tap each morning before use.

The South Waikato District Council drinking water is described as soft water, because there is less calcium and magnesium content. As a generalisation, soft water is deficient of minerals whereas hard water is richer in minerals. Soft water is slightly more acidic than hard water, and as a result it dissolves metals more easily/quickly.

In New Zealand, the plumbing materials/fittings (ie, your taps) which come in to contact with water are usually the source of heavy metals, such as lead, nickel, cadmium, copper and antimony.

When you turn a fitting off there may be a small amount of water left sitting in it. Whilst our treatment processes adjust the pH to reduce the water’s aggressiveness on pipework and tapware, there is the potential that water sitting in a plumbing fitting, if unused for several hours, may accumulate minute traces of metals.

Although the health risk is negligible, we recommend that you flush a mugful of water from your drinking-water tap each morning before use. This should remove any water that was left in your fittings, and metals that may have dissolved from the plumbing fittings.

All households are advised to take this precaution, whether they are on public or private water supply.

How do I tell if my fittings will accumulate small traces of metals?

Typically in New Zealand it’s the older plumbing/fittings, which come in to contact with water that are usually the source of heavy metals, such as lead, nickel, cadmium, copper and antimony.

If you want to know more about your fittings check with your plumber, or you can contact SWDC on 07 885 0340.