Section B Water Services

This Part sets out the requirements for the design, construction, installation, replacement, repair, alteration and maintenance of any part of a cold water service of a property that is connected to the drinking water supply, from the point of connection to the points of discharge. For the avoidance of doubt, the point of connection includes any tanks used for the collection, storage and supply of drinking water.

After B1.2(c) insert Tas B1.2(d) and (e) as follows:

This Part is an addition to the Deemed-to-Satisfy Provisions of Part B1. It sets out the requirements for pre-fabricated and constructed on-site cold water storage tanks used in a drinking water supply system.

This Part applies to tanks including rainwater tanks connected to the roof plumbing system, or a tank supplied from a nearby stream, bore or well used in drinking water services or drinking water supply in reticulated or non-reticulated areas.

Installation of cold water storage tanks used to supply water to a drinking water service must comply with this Part. For connection of cold water tanks where reticulated supply is available refer to Sections 8 and 16 of AS/NZS 3500.1 and Clause 2.16 of AS/NZS 3500.5 (as appropriate).

Cold water storage tanks and their installation must comply with the relevant requirements of the following documents:

Information on some of the above items may be obtainable from the manufacturer or supplier of the product or materials.

In addition to the marking requirements set out in clause 8.9 of AS/NZS 3500.1 all tanks must be permanently marked with the following:

A sludge valve must be fitted when the capacity of the tank exceeds 500 L. The minimum size of the valve must be not less than half the outlet pipe size nor less than DN 40.

Explanatory information:

Rainwater for drinking purposes should not be collected from recently painted roofs (until after the first few rainfalls), timber roofs preserved with chemicals, roofs coated with lead flashings, lead-based paints or tar-based coatings, or parts of roofs near flues from solid fuel heaters. Rainwater for drinking water purposes may be collected from roof types other than those identified above provided the roof and associated gutters are kept clean of leaves, animal remains, dust and other debris. Gutters must be kept clean by installing screens or leaf diverters between the roof and the water tank. The system should incorporate a 'first flush system' or other diversion system that will prevent the first flush of water from entering the tank.

All openings to tanks must be sealed so that insects, small animals, birds and sunlight cannot enter tanks to minimise the growth of algae and to prevent unauthorised access.

Tanks should be regularly maintained by cleaning out accumulated sludge from the base every 2 - 3 years. For detailed advice on desludging and maintaining tanks refer to the enHealth Guide – Guidance on the use of rainwater tanks; or HB 230 Rainwater tank design and installation handbook.

Before using the water from a tank for the first time the tank must be cleaned and disinfected (See Appendix I of AS/NZS 3500.1).

For ongoing maintenance of water quality one or more of the following water quality treatment methods should be adopted:

Chlorinating: To commission the tank sufficient chlorine should be added to provide a free chlorine residual of 0.5 mg/L after 30 minutes. To satisfy chlorinating requirements an initial dose of 5 mg/L of chlorine may be necessary. For every kL of water in the tank, add either: 40 mL of liquid pol chlorine (sodium hypochlorite - 12.5% available chlorine); or 8 grams of granular pool chlorine (calcium hypochlorite - 65% available chlorine). To calculate the tank volume in kL for a cylindrical tank the volume in of water in kL = D x D x H x 0.785. Where D = diameter of the tank, and H = depth of water in the tank in metres. To verify this calculation, compare this volume with the maximum capacity of the tank. The chlorine residual may be tested with a swimming pool test kit or dip strips. Water after chlorinating should not be used for 24 hours to enable any harmful microorganisms to be killed off.

Filtration: If filters are used in drinking water installations they are to be certified to the relevant Australian Standard under the WaterMark Certification Scheme and should be maintained by following the manufacturer's maintenance instructions.

Ultraviolet Disinfection: Filtration may be required to address water turbidity to enable adequate UV disinfection. Ultraviolet treatment is affected by the levels of turbidity, organic content from suspended solids, pH, hardness and UV transmissivity of the water. The intensity of the UV light and the build-up of suspended solids on the quartz tube affect the disinfection performance. Regular monitoring of the quartz tubes is critical. Lamps also need to be replaced regularly in accordance with the manufacturer's instructions.

The manufacturer's warranty must contain the following statement: This tank has been manufactured for the storage of drinking water and all materials used are suitable for contact with drinking water.