Guidance on use of rainwater tanks

Pipework

Page last updated: March 2011

Pipes that may be in contact with rainwater for extended periods of time should comply with AS/NZS 4020. In general, this does not apply to guttering or downpipes that deliver rainwater directly into the top of tanks because the contact with the rainwater is transient. However, underground pipework delivering water to the tank, between tanks or from tanks to houses should comply with AS/NZS 4020. Polyethylene pipes that are used in situations where the pipework is operating under pressure should comply with AS/NZS 4130.

Irrigation piping should not be used as it can contain and release lead into water at concentrations exceeding those specified in the ADWG.

The slight acidity of rainwater and its lack of buffering can make rainwater quite corrosive to plumbing. A long-term unpublished study by NSW Health showed that the water standing in metal pipework overnight frequently showed lead and copper concentrations above ADWG values. Flushing the water for three minutes removed this problem, except where lead was present in the catchment area. Shorter flushing times would probably work for smaller buildings.