Rainwater Harvesting
Rainwater is a good source of water for use on your garden. It can also be used for washing your clothes, and flushing the toilet. If it’s properly treated or purified rainwater can be used for drinking and other household uses. Installing a rainwater tank is relatively simple and inexpensive.
Uses of stored rain water
Stored rain water is most often used for homes that have no piped supply. It can also be used in addition to a piped supply (for irrigation, toilet flushing and other house hold uses). For drinking it is highly recommended that the water be treated or filtered.
Collecting and storing rain water can:
· reduce water costs for users on a metered water supply
· reduce demand on local authority water supplies and storm water disposal systems
· provide an independent supply for watering the garden in times of drought
· provide an emergency supply
· be the sole source of supply to house holds not on pipped supply
· reduce the rate of storm water run-off, easing erosion concerns
Levels of use
There are 3 main levels of use. They vary in price for each stage.
1. Simple rainwater storage tank for garden irrigation. A simple rainwater tank that can supply water by piping water directly from the guttering into a storage tank to use on your garden or lawn.
2. Rain water storage system for irrigation and toilet flushing. Rain water is piped into a large water tank from the guttering and is then pumped into the toilet cistern from the tank and used for flushing and also a tap on the water tank to use for garden irrigation.
3. Complete supply. This is the largest system, which is perfect for a beach Bach or holiday house. First the water is collected from the gutter, all guttering is recommended to have a leaf guard, rain water goes into the large water tank with a filter system to stop bugs and leaves getting in. Water is then pumped through the house to use for things such as the toilet flusher, kitchen sink, washtub, washing machine and garden irrigation. It is recommended that such as system be hooked up to the mains to top up the water tank when necessary
Safety
Rainwater can contain:
· campylobacter, giardia, cryptosporidium, salmonella and E.coli
· bird, possum and other animal droppings
· heavy metals such as lead from your roof
· ash and chemical residues - for example, from agricultural spraying and vehicle emissions
· leaves, soil and other debris.
To protect your health, you’ll need to ensure your rainwater system is property set up and maintained. Rain water systems need to be designed and maintained properly to avoid contamination of potable water supply The Ministry of Health recommends that where NO mains supply is available specifying a water filtration system for drinking water is highly recommended.
Water from roofs can be contaminated by:
· decaying vegetable matter such as leaves and petals and pollen (this can make the water more acidic)
· fecal matter from birds, possums and rats
· dead insects, birds and animals
· particulates from solid fuel flues, pollution
· in rural areas, chemical spray drift.
Legal requirements
If you are considering a large rainwater system you must keep in mind the following:
If you’re connecting a rainwater tank to your household plumbing, you’ll need a building consent. You may also need a consent to install the actual tank.
Some councils will only let you use rainwater for drinking and some other household uses if it has been treated. Some will require you to have your rainwater collection system inspected annually.
If you’re connecting a rainwater system to the plumbing of a house that also has a mains supply, you’re required by law to ensure that the mains water is isolated from the rainwater system. This is achieved by using a ‘dual check valve mechanism’ or a back flow prevention device. A qualified plumber must install this and a building consent is required. You may also be required to have annual checks on this device.