Design a safe water supply system that meets building users’ requirements while also making efficient use of water, energy and materials.

All habitable buildings must have a water supply that is potable(drinkable). That water supply must be protected from contamination, and must not contaminate the water supply system or source.

As part of that water supply system, the building must provide appropriate facilities for personal hygiene, and washing utensils, and hot water that is safe and will not cause scalding.

All water must discharge to a wastewater system to safeguard people from illness and protect them from odours and waste matter.

Water use

A recent survey of water use in New Zealand (reported in BRANZ Study Report SR469) found that the median daily water use was:

• in winter, 159 litres per person and 435 litres per household
• in summer, 231 litres per person and 504 litres per household

Water metering is now present in more than half of all New Zealand homes. Less than 10% of surveyed households had a rain tank of any size.

Sustainability considerations

While the first consideration in designing a water supply system is the building occupiers’ health and safety, it is good practice to design systems that support efficient and sustainable use of water, energy and materials.

By designing, building and renovating homes that use water efficiently, you can help to keep costs down, and benefit the environment by, for example, reducing the need to draw more water from rivers and waterways, reducing demand for energy, and reducing the need to build new infrastructure for supply and disposal.

There are sustainability considerations in most aspects of water supply, including decisions about the sources of water, location and layout of pipework and storage, materials used, heating methods, and appliances and fixtures specified.

As well as ensuring the building owner is aware of the impact of their behaviour, water use can be minimised by controlling water pressure, ensuring the hot water system is efficient, controlling the amount of water used for toilet flushing, reducing water flow from outlets, specifying efficient appliances, and minimising outdoor water use.

Addressing the problem of water supply and hot water systems leaks in existing houses is also important. The 2015 BRANZ House Condition Survey, involving over 500 randomly-selected houses, found leaking taps or shower heads in 7.5% of owner-occupied bathrooms and 5.6% of rental bathrooms. The numbers can be extrapolated to 147,000 houses across New Zealand. A leak of just 10 drips per minute from a single source is a loss of 3 litres per day or 90 litres per month.

Water meters

A report by New Zealand Infrastructure commission/Te Waihanga, Introducing water meters: Lessons and perspectives, found that “We all pay for our water and wastewater services, even if we don't always realise it. Metering water and charging for its use (volumetric charging) has helped many communities get more value from their existing infrastructure.”

Two significant benefits of introducing water metering are:

• It can help reduce the need for expensive work on infrastructure. Where water metering was introduced in Tauranga, it allowed the Waiāri Water Supply Scheme to be deferred by more than 10 years, despite high population growth - saving an estimated $53.3m.
• It can help locate and reduce the number of leaks. In New Plymouth, improved leak detection enabled by water meters had saved the equivalent of 68 Olympic swimming pools of treated water a year, half-way through the installation programme.

 

Updated: 28 November 2024