Implementing water efficiency measures in planning policy could help save Australia billions of dollars, improve water resilience and help reduce the emissions of housing stock, according to the Rainwater Harvesting Association Australia, but most state governments are dragging the chain.

Citing work from Dr Peter Coombes from Urban Water Cycle Solutions, RHAA executive officer Michael Smit said that applying water efficient measures, such as rainwater harvesting systems, into new buildings in Victoria could reduce the net present costs of water cycle management to 2050 by $6 billion, and save $3.5 billion in South East Queensland between now and 2056.

Savings break down

Speaking  to The Fifth Estate, Dr Coombes said: “When you turn the tap on in your house, it comes from a dam or another water source through big pumps and pipes and storage reservoirs until it gets to your house. The water you don’t use is then discharged by another set of pipes and infrastructure to the wastewater system.

“But if you put a rainwater harvesting tank on that house, you’re using rainwater rather than getting it from the water supply system. That means a certain proportion of water is no longer travelling through all the centralised water infrastructure, so you’re deferring that cost, and that saves money.”

For example, water prices in Brisbane are currently around $3.40 for 1000 litres, but the cost of supplying water to different parts of the city, including storage, pumping, treatment and testing, means the real cost of delivering water could be over $8 a kilolitre. If the cost of delivery was taken out of account, it could save $4.6 per kilolitres.

Mr Smit said: “If the marginal cost of rainwater harvesting paid by the homeowner is $2.50/kL there is a significant community benefit. The small benefit at a household scale becomes considerable at the neighbourhood scale, significant at a city scale and massive at a regional scale measured over 20 or 30 years.”

And, as well as cost savings in delivery, rainwater harvesting could also reduce stormwater infrastructure costs and flood damage by “millions of dollars”.

Dr Coombes said rainwater tanks were “storing water, rather than it being runoff into the system”, which also helped to protect waterways and wetlands.

“So there is a double benefit of changing behaviour.”

Lack of state action

Mr Smit has argued that the financial and environmental savings that can be had from rainwater harvesting could be realised if states implement water and energy saving targets to all new buildings and significant renovations.

However, only NSW to date has implemented such a policy – through the Building Sustainability Index (BASIX, which sets sustainability targets for water and energy as well as minimum performance levels for the thermal comfort of new developments).

To date, BASIX has resulted in rainwater harvesting being implemented in 90 per cent of all new dwellings in NSW and delivered a 40 per cent water and energy saving in building performance since 2004.

Why states aren’t motivated to act

So why have other states been dragging their heels? According to Dr Coombes, most states are aware of the findings, but are not motivated to implement such a scheme.

“No one analyses the whole system together; it’s partial accounting,” he said. “The states are more interested in the revenue earned from water monopolies than counting for the full cost of what they’re doing.

“Water companies don’t have to worry about how much things cost because someone else picks up the tab… Customers just get a price increase from the regulator and mums and dads pay for it.

“But I’ve worked out that in each of the capital cities, these [rainwater harvesting] ideas will reduce the water demand by a fair bit, thereby reducing the revenue earned by the water monopolies. It could reduce the cost by twice as much.”

He added: “Most states know about this work, but it needs to be higher profile because it’s something we need to do as a nation. The BASIX program shows that. But to do that, you need to take a whole society perspective rather than revenue.

“It takes a pretty strong public-based conversation to get to a better answer for society.”

Sustainable Buildings policy outline

As such, the RHAA, backed by Dr Coombes, is calling on state governments to implement a Sustainable Buildings policy.

This would include:

  • a 40 per cent reduction in mains water use as compared to 2013 levels in all new and significantly renovated dwellings
  • a 25 per cent reduction in demand for grid electricity as compared to 2013 levels for all new and significantly renovated dwellings.
  • a state environmental planning policy that stipulates water and energy targets for dwellings, supported by a simple web-enabled planning approval tool and model design guidelines
  • an evidence-based planning policy to avoid substantial economic costs and environmental impacts
  • independent monitoring and assessments, including annual reviews and progress reports.

“A public responsibility to promote this policy”

Mr Smit said: “Australia will need to build about four million new households by 2036, a 50 per cent increase from 2011.

“We suggest that those houses should be considerably better than the houses we build now and that there is an existing low risk policy to achieve this. Given the public savings are measured in the billions of dollars we believe we have a public responsibility to promote this policy.”

Dr Coombes added: “From my findings, I fully agree with the need to have a national conversation about this. It’s more than just about the revenue and single infrastructure agenda of a small group of organisations.

“We need a water policy discussion in place that represents more of society.”

It appears that state governments are already sitting up and taking note, with Queensland’s water minister Mark Bailey reportedly calling a departmental briefing on the findings of a report last month.

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  1. The use of rainwater tanks at the residential scale as part of a sustainable building approach can have many advantages beyond a narrow water supply focus.
    Many Councils require new development to implement On Site Detention as part of their engineering requirements to protect downstream drainage infrastructure, and in many cases offer credits for plumbing tanks to suitable high yield demands. Reducing the volume of runoff in frequent, lower intensity events can limit the potential for waterway erosion- harvesting rainwater is a complementary strategy to assist this. And if overall runoff volumes are reduced the effectiveness of other stormwater treatment measures can be enhanced (less chance of these going into bypass). Finally, tanks offer a spatially efficient method to manage runoff, and when land take/ value for other treatment approaches is taken into account can support more cost effective designs.
    In all jurisdictions is a requirement to acheive environmental standards, and with our ever growing cities and increased impervious surfaces stormwater runoff is seen as a major threat.
    It is narrowly focussed to dismiss tanks as costly just because they have a long water yield payback, or to say they will fall into disrepair and therefore cannot form a legitimate part of the solution, or that the energy consumed by rainwater pumps is excessive while we invest in desalination and transport water tens if not hundreds of kilometres.
    Done properly, sustainable buildings offer a paradigm shift in how our urban growth and built form support a future economy in a climate stressed world, and it should be seen as an opportunity.

  2. Every study we’ve done in a water retailer in Melbourne shows rainwater tanks to be one of the most expensive sources of water. The home owner will be lucky to get their money back in less than 20 years. It’s probably over 30 years in most cases.

    Academics talk about the environmental benefits of rainwater tanks but these are difficult to quantify and even more difficult to cost. The energy to pump rainwater for household use is often much more than for a centralized supply system on a per kL basis.

    I don’t believe that potable water is Brisbane cost $8 per kL to produce while it is sold at $3.40. So who is subsidizing the water company there with such mind-boggling generosity?

    The States are not as ignorant or inefficient as this article makes out. Victorian regulations require new homes to be constructed with either a rainwater tank or a solar hot water heater with the latter being the more popular choice. To mandate tanks on those who don’t have an emotive feeling for them is a waste of funds. They don’t bother to maintain their tanks so once the pump breaks down, it sits there like a white elephant.

  3. In Victoria since 2007 some inner city councils have been implementing SDAPP – Sustainable Design Assessment in Planning Process and using the STEPS and SDS tools which are similar to BASIX. The BESS tool is now taking over and all tools integrate the Melbourne Water STORM tool. To achieve 100% on STORM which result in a 45% reduction in nitrogen, most applicants use water tanks connected to toilets.
    So, many high rise buildings in the inner city have a large water tank connected to the ground and first floor toilets. In Darebin where I work about 90% of developments of 5 or more units have committed to water tanks connected to toilets. This includes 5 units on a block where the was one house and high rise apartments. This is great for reducing potable water use, reducing stormwater flows to local pipes (which will cost councils millions to replace) and reduces pollution to local creeks and the ocean and we all benefit from that!

    Recently 6 councils had a ESD policy passed by the state Government which includes water. Another 3 are expected to follow. It is hoped this will lead to a state wide policy.\

    There are 18 local councils who are members of CASBE – the Council Alliance for a Sustainable Built Environment and water and stormwater are integral to our vision. All these council are at various stages of implementing the SDAPP process into planning. Where federal and state governments have failed, local government has moved ahead.

    And desalination plants are extremely expensive to build and use outrageous levels of energy to operate. More energy = more pollution.

    Maybe we need to think less about pay back periods for individual water tanks and be good citizens and think about the broader costs – economic, social and environmental.

  4. Thank you to the fifth estate for publishing this important article. Chris Walsh’s website and provide critical real information about water efficiency and retention of rainwater. Regarding the need for sustainable buildings in WA – our work shows that rainwater harvesting in Perth refills a 5 kL rainwater tank from 5 – 30 times dependent on rainwater use. Indoor use of rainwater drives greater yields and increased protection of waterways – Yes this happens mostly during 9 months of the year but this local harvesting allows regional reservoirs to fill more quickly, more stream flows in rivers and reduces dependency on desalination and aquifers. This is an important discovery – local rainwater harvesting complements and is linked to centralised supply – producing an overall more beneficial outcome for everyone – in this situation the best performed rainwater harvesting system is drawn down as often as possible to increase benefits to the security provided by the centralised system

  5. Dear Chris Walsh – the article you linked shows what can be done with recycled water. What it doesn’t do is show the cost of the system installed and expected payback period. I am also very sceptical of the calculator they used for water saving. That surely depends on the yearly rainfall which in Victoria varies wildly from year to year. I agree that desal plants are the way to go for the city, particularly if we found the way to power them through solar or wind. If you want to make a contribution it is actually better to separate the grey wastewater and use it for landscaping. In a typical house production of grey waste water is a reasonable constant. Rainfall is not. Another problem with the rainfall is that you need the most of that collected water when there is least of rain (summer in Victoria). Nobody waters the garden after rain (when your tank is full)

  6. I can see the community benefits of rain water tanks. However, at the individual householder level, with the current water pricing, the payback for a rainwater tank is not realistic. I have worked in project home building companies and built sustainable display homes including a zero water home. Costing studies on the zero water home have shown that while energy conservation measures do have realistic paybacks, rain water/grey water recycling systems are no where near and about the time frame mentioned in the comment above. Due to rise in energy prices, the energy paybacks are more attractive. Similar has to happen with water.

  7. Small household water tanks are expensive tokenism which make the owner feel good but achieve little else. Using the example above if water costs $2.50/kL and the house has a 1000L (or 1kL) tank then it stores $2.50 worth of water. Even if the tank is turned over 10 times a year (very optimistic) then the savings are $25/year. Would be lucky to pay the cost of the tank over 30 years as this is only $750 in water value. Would be also interesting to see how much water is required to make a plastic or steel rainwater tank – suspect that it may well be negative.

    It would be cheaper to desalinate seawater than install millions of very small water tanks – there is plenty of seawater to go around especially it is eventually replenished (hopefully) by treated waste water and natural runoff.

    BTW I have a 110,000L rainwater tank but this is because I don’t have mains water. You need this size of tank if you are going to supply a household and get through a WA summer.