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Ensuring that products are safe for use in contact with drinking water

Every day, millions of Australians turn on the tap without much, if any, thought about whether the water that will flow is safe to drink. Trust in the supply of safe, clean drinking water by utilities nationwide is high, an expectation for people living in developed countries.

Products that can impact the quality of the water flowing out of taps across the country are the focus of AS/NZS 4020:2018 standard for ‘Testing of Products for Use in Contact with Drinking Water’.

The Standard was developed to specify the requirements for the suitability of products and materials for use in contact with drinking water.

The Standard ensures that products that are in contact with drinking water do not introduce substances into it that cause a deterioration in its quality or jeopardise public health. For these reasons, the Standard requires that products do not affect the taste or appearance of water, nor support the growth of microorganisms or release cytotoxic or mutagenic compounds or metals. The tests required are specific to the type of product submitted.

This Standard specifies some of the criteria that products must meet to qualify for WaterMark Certification. This Certification enables the plumbing industry to use products that meet the AS/NZS 4020:2018 standard and nationally recognised water quality standard values. It helps manufacturers, water authorities, and regulators to identify the performance that can be expected when purchasing a product to be used in the delivery of drinking water.

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

The products are assessed by exposure to test waters. After the product has been exposed to test water, a sample of it is extract and analysed in accordance with the specifications described in 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 temperature including water-heating systems.

The following list provides an overview of the tests associated with AS/NZS 4020:2018:

Taste

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

Appearance

Water extracts are analysed to determine 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

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

The Ames test is a reverse mutation assay. The test is used to determine whether elastomeric products, or products containing elastomeric components, 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.

Metals

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

Organic Compounds

Water extracts are analysed for organic compounds using USEPA methods. The limits are in line with the Australian Drinking Water Guidelines.

In the past 25 years, the Australian Water Quality Centre (AWQC) has tested more than 4l,000 products in accordance with the Standard. Examples of the products and materials tested to the Standard are described below.

TABLE 1:  PRODUCTS AND MATERIALS TESTED TO AS/NZS 4020

Product

Materials

Pipes/Tubes

Polybutylene, Polyethylene, Polypropylene, PEX, Copper, Stainless Steel, Cement

O-rings

EPDM, Nitrile, Natural Rubber, Silicone, NBR

Gaskets

EPDM, Nitrile, Natural Rubber, Silicone,

Water Connectors

Polypropylene, HDPE, Brass

Filter Housings

Polycarbonate, Acetal Copolymer, Polypropylene

Sink Mixer Components

Brass, EPDM, Nitrile, Natural Rubber, Acetal

Olives

Acetal, Brass

Flexible Hoses

EPDM, Soft PEX

Hoses (dishwasher)

Plastic PVC

Jumper Valves

EPDM, Nitrile, Natural Rubber, Acetal

Note 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/NZS4020 provides an important step in assuring the suitability of products for use with drinking water.

Contact us to discover more about how we protect public health by providing manufacturers NATA accredited AS/NZS 4020 product testing and advisory services to ensure that their products meet the requirements for WaterMark Certification and so are safe for use in plumbing installations.

By Michael Glasson, the Australian Water Centre’s Supervisor Product Testing.