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Smart guide

Efficient use of water

By reducing the water flow from your taps and showerheads, you'll save on hot water.

Using less water is easy

Many older style taps and showerheads use a lot more water than is needed for the job they do. There are simple, inexpensive ways to use less water and save money, without compromising on performance.

What is water flow?

Water flow is the rate – in litres per second  at which water comes out of your tap or showerhead. It shouldn't be confused with water pressure, which is the amount of force (from gravity or pumping) pushing water through the pipes. Water pressure is measured in kilopascals or kPa.

The water pressure in your home determines what type of hot water system you can have, but your tapware or showerheads determine the flow.

How much water do you need?

You need about six litres of water per minute from hand basin or kitchen taps. Modern showerheads can give you a great shower using six litres of water per minute (or even less). This is because they pull air into the water stream instead of dropping flow and pressure so the water droplets are hollow. You get the same feeling of a full-pressure shower but with a lot less water flow.

Consumer NZ tested water-efficient showerheads in 2010. They found replacing a 12-litre per minute showerhead with one that flows at eight litres can cut your hot water bill by about $150 a year while still giving you a comfortable and effective shower.

From April 2011 taps and showerheads have to be rated under the Water Efficiency Labelling Scheme (WELS) – look for models with three stars or more.

Compare water efficiency ratings for products on the Australian Government's Water Rating website.

Benefits of reducing water flow

By reducing the flow of water from your taps and showerheads you'll use less water for every minute the tap or shower is on. Using less water will reduce your water heating bill, and if you're on metered water your water bill will be lower too. If you’ve got a hot water cylinder, reducing the flow of water will make your hot water will go further.

Measure your flow rate

To check flow rates from your taps and showerheads:

  • Turn the tap or shower mixer on full and run the water into a bucket for 15 seconds.
  • Measure how much water you have in your bucket, then multiply this figure by four to get your flow rate per minute.
  • A flow rate of more than nine litres per minute in your shower and six litres per minute from your taps means you are probably using more water than you need.

How do you reduce the flow?

Apart from just not turning the tap on fully, there are three things you can do:

  • Fit flow restrictors to existing taps and shower mixers. These cost from about $15 (2017 price). Check your brand of tap or shower mixer and ask your plumbing retailer for advice on which size. Aim for a flow of six to nine litres per minute. Depending on the design of your basin or shower mixer you may need a plumber to install these.
  • Fit aerators to kitchen taps. These simulate high pressure by dragging air through and cutting the flow of water from your tap by 50 percent without reducing water pressure. They are inexpensive and easy to install.
  • If you have a very strong shower, have your plumber fit a pressure-limiting valve to reduce flow to the whole plumbing system.
  • Replace tap fittings and showerheads with water-efficient fittings. Check the WELS label for the most efficient models. Showerheads with a three-star rating use no more than nine litres of water per minute, whereas traditional showerheads use between 15 and 20 litres.

    An efficient showerhead can save 50 litres of water for each six-minute shower. Fixed showerheads are often easy to replace, by simply unscrewing them. New three-star showerhead prices start at about $20 (2017 price).

Get advice from your plumber, plumbing retailer or eco design advisor (see the Eco Design Advisor website) about which options are best for your household and who can install them. The best option may depend on what type of hot water system you have and what pressure your hot water is delivered at.

Water your garden wisely

In the summer months, water use typically doubles in urban centres. This is the season when the kids make water slides on the lawn, the swimming or paddling pool needs filling and the garden needs watering.

Summer demand places stress on water supplies. Some councils place seasonal or even year-round restrictions on lawn and garden watering.

By applying some of the ideas here, your garden will survive the hot, dry weather and you will minimise wastage of treated drinking water (you can also reduce the size of your water bill if you are in area with volumetric charging).

Choose appropriate plants

Where possible, choose plants suitable for your climate. Plants that naturally grow in your area are generally adapted to the local conditions and should not need watering once they are established. Using native plants is the easiest way to achieve low maintenance, a water-efficient garden and encourage native birds.

Group plants with similar water demands together so that you can limit the areas that you need to water – you’ll waste less water on plants that don’t need watering.

Watering tips

Summer peak demand for water is largely due to lawn and garden watering. With the following tips, it's easy to use less water and still keep your lawn and garden healthy.

Use rainwater

If you are on mains water supply, you can still collect rainwater from your roof for use on your garden.

Collecting and using rainwater has more information.

Avoid watering in wet/humid weather

Before watering, take into account the weather that week. Has it rained? What was the average temperature and was it windy? What was the humidity?

All of these things have an impact on how dry your garden will be and how much top-up irrigation is needed. You can check the rainfall yourself by leaving a measuring container outside (empty it each week).

Water gardens in the morning and on calm days

If you water your garden in the early morning, you reduce the risk of the sun evaporating the water and scorching plant leaves. Watering on calm days will also prevent evaporation and minimise wind drift.

Choose the right irrigation system

Irrigation systems that water into soil, rather than onto plants, are more efficient  they ensure plant roots grow deeper and are more resilient to dry conditions. A dripper irrigation system is ideal for regular watering. A soaker hose under mulch placed at the base of plants is also effective. These options are much more efficient than using a sprinkler.

Other tips:

  • Water plants at a lower rather than higher pressure to avoid runoff and ensure the soil absorbs the water.
  • Regularly check your irrigation equipment or hose for leaks or blockages.
  • Remember to turn off automated irrigation systems when it rains.

Looking after your lawn

Plant your lawn in early autumn or spring. This gives the lawn chance to establish a good root system before summer.

Watering lawns

Here are some water saving tips for lawns:

  • Avoid mowing the lawn when it’s very dry or very wet.
  • Don't cut your lawn too short or too often in summer – if you set the mower to about 6-8cm the lawn's roots will be shaded and the grass plants will be less stressed.
  • Aerate your lawn in the early spring or autumn to improve water absorption (push a garden fork into the lawn at intervals). Afterwards, apply a thin layer of compost or other suitable organic material and rake to distribute evenly.
  • If you leave grass clippings on the lawn every so often, this will return nitrogen  a vital nutrient  to the soil and the added organic matter will help prevent moisture loss.

In dry weather your lawn may start to turn brown. This is a dormant state. Most lawns recover their lushness soon after sufficient rainfall returns.

Looking after trees, shrubs and flower gardens

Here are some water-saving tips for trees, shrubs and flower gardens:

  • Direct water to the roots of plants and shrubs.
  • Plants have different watering requirements at various stages of growth. Water according to their needs.
  • Water deeply but slowly and infrequently (twice a week, and no longer than 30 minutes each time) to toughen plants and encourage plant roots to grow deeper looking for moisture.
  • Dig compost into the soil in the autumn or spring to improve soil. Or layer it on top and allow earthworms to do the work.
  • Use bark, compost, pea straw, lawn clippings or other organic material to mulch around plants and trees. This retains moisture in the soil, reducing watering and the impact of drought.
  • Grass under a tree competes with the tree’s roots for water  remove grass and use mulch instead, being careful to keep it from touching the trunk.
  • Plant a shelterbelt or trees to provide shade and wind protection to reduce evaporation and the need for irrigation.

Pools

To reduce evaporation and water loss:

  • cover swimming and spa pools when not in use (ensure children can't get under the cover by meeting pool barrier requirements – see MBIE's Building Performance website for more on Restricting access to residential pools
  • check valves yearly if they automatically top up the pool. A faulty valve can waste a lot of water
  • don't empty pools unless absolutely necessary  some pools will crack or pop out of the ground if emptied. If you have to empty a pool, check with the manufacturer or a pool maintenance professional first.

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Other resources

  • Building Code requirements: Water supplies

    MBIE’s Building Performance website explains the Building Code clause G12 requirements for the safe supply, storage, reticulation and delivery of water.

  • Local council: Water

    Your local council can provide information about water restrictions, rainwater collection systems and any schemes they have to help you save water. This website has contact details for your council.

  • Water efficiency labeling scheme

    You’ll find an introduction to the New Zealand water efficiency labelling scheme on the Ministry for the Environment website.

Note that this document is published by the Ministry of Business, Innovation and Employment Chief Executive as Guidance under Section 175 of the Building Act 2004. This is a guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case.