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according to the manufacturer’s instructions. Dose the tank and leave for 30 minutes before running the dosed water through all household lines until clean water has come through all taps.
Another method of treating water is with UV light. A tube containing a UV bulb is inserted in the water. The light disrupts the DNA of micro- organisms so they are unable to reproduce. In order to be e ective, UV light must pass through water that is relatively clear and free of particles, so a ltration system must be installed upstream of the UV light.
Roof maintenance and painting
Roofs used as water catchments must not be painted with lead or chromium-based
paints. The use of paint containing white lead was banned in New Zealand in 1979, but some special-purpose, lead-based paints containing red lead are still available. These should be clearly labelled. Anti-rust primers sometimes contain chromium salts.
Most modern roof paints are labelled for their suitability if the roof is to be used as a water catchment, but if unsure, always ask the manufacturer.
The roof should be cleaned annually. Before beginning, disconnect pipes to the water storage tank so the water can be ushed away. Scrub the roof with a brush or broom and clean water. Clean and rinse through the spouting to remove dirt, debris and contaminants.
Useful publications
The Ministry of Health in association with
the Health Promotion Agency has published resources on the safe collection and storage of drinking water from roofs, including:
● Water collection tanks and safe household
water, available from www.healthed.govt.
nz/home
● drinking water guidelines, available at www.
health.govt.nz.
The BRANZ Level website (www.level.org.nz/ water/water-supply) also has information on: ● harvesting rainwater
● storing rainwater
● ltration and treatment.
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