3.4.5 Materials and chemicals

Summary of actions

• Ensure that only approved materials and chemicals are used.

• Establish documented procedures for evaluating chemicals, materials and suppliers.

The selection of materials and chemicals used in water systems is an important consideration as potentially they may have an adverse effect on drinking water quality. Chemicals added to water include disinfectants, oxidants, coagulants, flocculants, algicides, antioxidants and chemicals for softening, pH adjustment, fluoridation and scale prevention.

All chemicals used should be evaluated for potential contamination. General considerations include data on impurities, chemical and physical properties, maximum dosages, behaviour in water, migration and concentration build-up. In addition, the potential impact of water treatment chemicals on materials used in treatment plants needs to be considered. For example, ferric chloride used as a coagulant is extremely corrosive and can have severe effects on commonly used grades of stainless steel.

Chemical suppliers should be evaluated and selected on their ability to supply product in accordance with required specifications. Documented procedures for the control of chemicals, including purchasing, verification, handling, storage and maintenance, should be established to assure the quality of the chemicals at the point of application. Responsibilities for testing and quality assurance of chemicals (supplier, purchaser or both) should be clearly defined in purchase contracts.

Contaminants may also be introduced when water comes into contact with materials such as filter media, protective coatings, linings and liners, joining and sealing products, pipes and fittings, valves, meters and other components. Materials used should comply with Australian Standard AS/NZS 4020 Products for use in contact with drinking water.

The products used in water systems should be subjected to an audited system of quality control.