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Components of a Water Supply

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There are several key parts to a typical water supply. These include: source, inlet/suction pipe, well-head or bore-head, backflow prevention, storage tank(s), filtration and water treatment and reticulation.

Water sources

There are different types of water sources:

  1. Ground water (aquifers):
    1. Deep secure ground water. These sources are protected from the influence of surface water contamination and are usually deemed to be safe.
    2. Shallow or insecure ground water. Shallow bores and wells are at risk of contamination and need to be filtered and treated.
  2. Surface water (general)
    1. Rivers, streams, creeks, water races and irrigation races. These open catchment sources are at risk of contamination and need to be filtered and treated.
  3. Roof water
    1. Older roofs may be at risk of leaching metals and lead from iron and lead based paint.
    2. All roofs are at high risk of contamination by birds, feral animals and rodents.

Well-head or bore-head protection

The well-head or bore-head is where the water is extracted from the ground. It should comprise a suitably designed and constructed concrete pad and be well sealed. This protects the bore and prevents any contamination from the surface, eg during rainfall periods, tracking down the outside lining of the bore and into the ground water.

Backflow protection

Backflow prevention is important, particularly on farms and on properties where commercial or industrial activities are being undertaken. Backflow prevention ensures that no contamination is able to backflow into the water source or the reticulation. There are different methods of backflow prevention. Examples are: air gap separation by ball cock, a range of back flow prevention devices depending on the water pressure and purpose. Back flow prevention systems and devices need to be maintained to ensure they are fully operational and effective.

Storage tanks

Many properties, particularly in the rural zones, have water storage tanks. These tanks store water for sustainability for domestic use and fire-fighting purposes.  It’s important that tanks are well-sealed to prevent the entry of birds, feral animals, rodents and insects from entering the tank and contaminating the water. Cracks around the top and unsealed lids need to be sealed. Breather holes need to be screened for insects.

Water filtration and treatment

Water from insecure ground water (shallow bores or wells), surface water and roof water will need to be filtered then treated. Filtration removes suspended matter (particles) from the water and this enables effective water treatment to remove harmful microorganisms such as bacteria (eg E.coli) and protozoa (eg Cryptosporidium and Giardia).

There are various types of filtration. These include cartridges, filter bags, candle filters, sand filters and reverse osmosis.

Filters require regular checking and maintenance to ensure they remain effective. Poorly maintained filters can create a risk of a build-up of bacteria and higher level of contamination. They can also inhibit effective treatment following filtration, making the supply unsafe for domestic purposes, including drinking.

There are various methods of water treatment. These include: Ultra Violet Light sterilisation, chlorination and ozone. The main method is UV light. Treatment systems such as UV light need to be of a suitable design and well-maintained. The UV tube sleeves can become soiled and stained and the UV light tubes lose their intensity and the ability to destroy bacteria. This makes the supply potentially unsafe.

Helpful links for further information

Where do I go for advice?

Environmental Health Officers – Selwyn District Council. Contact the council and ask to speak to the on call Environmental Health Officer.

Note: This is a 24/7 service

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