Why water matters
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Vicki Cowan
Why water matters
Behaviour, Blog, Water
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It’s an odd thing that while many people are vocal in their demands that councils reduce spending and angrily object to each rates hike, most use water as if it was an endlessly abundant resource and just arrived free of charge each time they turn on a tap.

Most people – unless they are charged for water separately – do not see the point of reducing the amount of water they use.
Our HomeSmart Renovation project was a case in point.  Water efficiency improvements were recommended as part of the Renovation Plan provided to participating households.  However,  few households saw them as a priority, and even fewer took measures to reduce water use in the home, even though they are often very easy to implement and cheap to install.  Interestingly, their perception of water use was very inaccurate.  71% of households thought they weren’t high water users, yet only 45% of monitored households actually met Beacon’s HSS High Standard of Sustainability® benchmark for water use. Unsurprisingly, the most water-efficient households were in areas that were metered and directly charged for water use, rather than paying an annual charge in their rates bill.

Convincing people to change

In fact, whether metered or not, we pay dearly for our water.  Treating water to drinking standard is expensive and the process also uses a considerable amount of energy, adding to the cost of provision and national/regional energy demands. Yet we only drink 3% of the water that runs from our taps.  The vast majority of expensive, treated water piped into our homes is used where untreated water would do the job perfectly well: in toilets, washing clothes and gardens.

Then there’s the wastewater we produce – it feeds into wastewater treatment plants that are expensive to build, run and maintain. If households used less potable water and collected stormwater for non-drinking purposes (which would also reduce stormwater spewing into drains), local and regional councils stand to make big gains.  So do ratepayers.

Typically, most councils spend about a third of their annual operating budgets on delivering and managing the three waters – potable drinking water, stormwater, and wastewater. That amounts to billions of ratepayers’ dollars each year.

This can be changed.  One Beacon study found that, as a result of implementing a water demand management approach, Tauranga City Council delayed the implementation of the next major water supply infrastructure identified for the city’s water supply, by approximately 10 years with a net benefit to the community of $53.3 million in 2009 terms.

Water efficiency is an easy win

Ironically, water efficiency is a relatively simple change to make.  It boils down to:

  • Changing to water efficient tapware – look for taps with a maximum flow of 4.5L/min.
  • Changing to water efficient shower heads – look for showers with a maximum flow rate of 9L / min
  • Installing dual flush toilets with a 4.5L full flush and 3L half flush
  • Selecting water efficient appliances – look for least 5 star WELS-rated dishwashers and washing machines

Given the low cost for water efficient fittings and the ease of incorporating them into homes, they should be a top priority for affordability of operating a house.

It is particularly important to include water efficiency measures when installing efficient hot water systems such as solar hot water or heat pump hot water or in converting to instant gas hot water.  Beacon’s experience in both new homes and retrofits, is that households who experience much cheaper and/or free hot water exhibit substantial takeback in terms of hot water use.  In one of our Papakowhai retrofits, the installation of the solar hot water system resulted in an increase of hot water energy use by the household of 21% between the 2007 and 2008 winter periods.

Water re-use

Several Beacon houses have used either rainwater harvesting or greywater systems.  Both have proved relatively straightforward and very worthwhile in terms of reducing demand on reticulated water.  The Waitakere NOW Home had a 13,500L rain tank plumbed for toilets, laundry, hot water and outdoor uses which supplied 52% of the household’s water needs and dropped their demand for reticulated water to only 85 litres per person per day.

The NZ Housing Foundation’s HomeSmart Home had a much smaller rainwater tank (4000L) plumbed for outdoor use and a greywater system plumbed for toilets.  The tank proved less effective, partly because it ran out during a dry summer and partly because it did not supply any indoor use.  The greywater system proved very easy to maintain and reused 30% of waste water from bath, shower and laundry.  Together with water efficient appliances and fittings, the tank and greywater system reduced the family’s water use to 117 litres per person per day.  This is a considerable saving in Auckland where water is metered.

In order for a combined greywater and rainwater system to be effective, we suggest that rainwater be plumbed into the laundry, hot water system and outdoor uses, with greywater supplying the toilets and/or outdoor use through an underground distribution system such as the Water Lillie.


For more information:

Beacon’s HSS High Standard of Sustainability www.beaconpathway.co.nz/being-homesmart/article/beacons_hss_high_standard_of_sustainability

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