Rainwater harvesting: what it is good for

Rainwater is not automatically safe to drink

Rain itself is relatively clean, but it collects whatever is on the roof, in the gutter and in the tank: bird and rodent droppings, dust, leaves, insects, and material from the roofing itself. Collected rainwater should be treated before drinking, and it is best used first for the things that do not require drinking water quality.

Good uses without treatment

Flushing toilets, cleaning floors and outdoor areas, washing vehicles, watering ornamental plants, and topping up laundry. In a long dry spell, covering these uses with rainwater frees your treated supply for drinking and cooking.

Setting up a simple system

• Roof. Avoid collecting from roofs with lead-based paint, asbestos sheeting or heavy bird activity.
• Gutters and screens. Keep gutters clear and fit a mesh screen to keep leaves and insects out of the tank.
• First flush. Divert the first few minutes of runoff away from the tank. That is the portion carrying most of the accumulated dirt.
• Tank. Opaque and covered, so light cannot drive algae growth and mosquitoes cannot breed. A covered tank is a mosquito control measure as much as a water quality one.
• Tap. Draw water from a tap above the tank floor so settled sediment is not disturbed.

If you intend to drink it

Treat it, and treat it consistently. Boiling is effective against organisms. Filtration can remove sediment and improve what the treatment then has to work on. If you intend to rely on rainwater as a drinking source over the long term, have it tested so you know what you are dealing with rather than assuming.

Maintenance is the part people skip

Clean the gutters, the screens and the first flush diverter before the rainy season, and inspect the tank for cracks, light leaks and standing sediment. A neglected system produces worse water than no system.