Keeping drinking water delightful

Australia has some of the best tap drinking water in the world. Here, Michael Glasson explains the Standard that ensures our drinking water tastes great, looks great and meets a range of other requirements that set it apart from other countries.

The Australian drinking water standard – AS/NZS 4020 Testing of products for use in contact with drinking water – was developed to assess the suitability of materials used in contact with drinking water.

Water authorities strive to maintain drinking water of a high standard for customers and cannot afford to introduce products that may jeopardise water quality into their supplies.

Consequently, there is a need to ensure products in contact with drinking water do not introduce substances that will cause a deterioration in quality.

A wide range of products are tested to the Standard including valves, pipes, coatings and end­-of-­line fittings which includes taps.

The Standard requires that products do not affect the taste or appearance of water; do not support the growth of microorganisms; and do not release cytotoxic or mutagenic compounds or metals. The tests required are specific to the type of product submitted.

The products are assessed by exposure to test waters. The exposed surface areas to volume test requirements are detailed in the Standard.

After the product has been exposed to test water, a sample of the test water extract is analysed in accordance with the specifications in each Appendix of the Standard. Scaling factors or dilution factors may be applied, depending on the end use of the product.

There may also be a requirement for hot water tests for products that are used at high temperatures including water­heating systems.

The following points provide a brief description of the Appendices that relate to the test methods associated with AS/NZS 4020:

Taste of water extract

Trained panellists taste water extracts to determine whether products leach compounds that impart a discernible taste.

Appearance of water extract

Water extracts are analysed for an increase in colour and turbidity.

Growth of aquatic microorganisms

The test is performed by immersion exposure with products examined for the ability to support bacterial growth by monitoring dissolved oxygen levels in water extracts.

Cytotoxic activity of water extract

Water extracts are tested for cytotoxicity using mammalian cell lines. An adverse effect on the health of the cells is recorded as a cytotoxic effect.

Mutagenic activity of water extract

The Ames test is a reverse mutation assay. The test is used to determine whether products release mutagenic compounds into water extracts. The water extracts are mixed with specific bacteria. Any change in the genetic nature of the bacteria is regarded as evidence of mutagenic activity.

Extraction of metals

Water extracts are examined for the release of Arsenic, Antimony, Barium, Cadmium, Chromium, Copper, Lead, Mercury, Molybdenum, Nickel, Selenium and Silver. The limits are in line with the Australian Drinking Water Guidelines.

In the past 22 years, the Australian Water Quality Centre (a business unit of SA Water, a South Australian government enterprise), has tested over 4,000 products in accordance with the Standard. Listed in Table 1 are a few examples of products tested to the Standard and the respective materials used.

It should be noted that similar products that are manufactured using different processes may have different performance characteristics affecting the ability of the product to leach compounds into drinking water.

The challenge for manufacturers is to produce commercially viable products that will not leach harmful compounds into drinking water, or compounds that alter drinking water, making it aesthetically undesirable.

Testing to AS/NZS 4020 provides an important step in assuring the suitability of products for use with drinking water.

Table 1. Products and materials tested to AS/NZS 4020.

For more information please contact the Australian Water Quality Centre on 1300 883 171.