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How to slash water use in high-rise buildings by 80 per cent

toilet sign
Photo by Franck V. on Unsplash

Water scarcity is a serious issue for densely populated cities, especially in Australia. Fortunately, technology can help us reduce huge amounts of water in our buildings, with the good old vacuum toilet leading the way.


Water scarcity is a growing issue. The World Bank predicts that by 2050, demand for water will increase by 55 per cent due to increased demand from urban populations.

Along with the possibility of running out of water, many world cities are sinking as a result of excessive groundwater extraction and the weight of high-rise buildings. Jakarta is sinking so quickly the Indonesian government has a 10-year plan to transfer all government offices to a new capital city.

But the responses to this growing crisis so far have missed the mark. For example, many cities have or are building energy-intensive, environmentally damaging desalination plants that dump saturated saltwater effluent into the ocean.

Sydney’s desalination plant supplies 15 per cent of the city’s drinking water but that capacity is destined to double soon at considerable cost to ratepayers.

A truly “smart city” shouldn’t rely on destructive, expensive technology when proven technologies, such as vacuum systems, are already available.

Melbourne Water’s head office in Docklands installed a vacuum system in 2013 for 1300 occupants and managed to achieve a rarely-heard-of NABERS Water rating of 6.0. Photo by Umow Lai.

The solution is “LeanWater”

The solution to the water scarcity problem is simple: use less. “LeanWater” is the new thinking for multi-storey and high-rise buildings, and is capable of reducing water use by 80 per cent.

The main goal of LeanWater is to create more value with fewer resources. Lean principles include price point, requirements and expectations. The result is less waste, reliability of service and meeting all regulatory requirements with improved operational performance.

It’s possible to save 80 per cent of water used by office buildings, multi-storey retail centres and hospitals by switching to vacuum toilets, which use 0.5 litres of water per flush compared with 4.5 litres per flush for traditional gravity toilets.

The vacuum technology is also superior to low-flush toilets that can exacerbate network blockages because they use less water, resulting in increased infrastructure charges.

Melbourne Water shows the way

The results speak for themselves. Melbourne Water’s head office installed a vacuum system in 2013 for 1300 occupants, and managed to achieve a rarely-heard-of NABERS Water rating of 6.0.

Based on the high NABERS Water rating, Bloomberg’s London team inspected the system at Melbourne Water’s head office and installed the same one in its Norman Foster-designed building for 5000 occupants.

Vacuum flush toilets were part of Bloomberg’s three-pronged approach to water efficiency, which scored the company the highest possible BREEAM assessment score of 100 per cent in water conservation.

Vacuum flush toilets were part of Bloomberg’s three-pronged approach to water efficiency, which scored the company the highest possible BREEAM assessment score of 100 per cent in water conservation.

According to Bloomberg’s project director Kathryn Mallon, its approach to water conservation is as follows:

  1. Use of water efficient fixtures, most notably, our vacuum flush toilets that use approximately 20 per cent of the water of a standard water efficient toilet (0.8 L/flush vs 5.0 L/flush).
  2. Capture, treatment and reuse of our grey water systems, most notably, our cooling tower bleed-off flows to serve the vacuum toilet system. The recycle of cooling tower water earned the project its second BREEAM Innovation point.
  3. Capture and treatment of rainwater from the roof. This rainwater would otherwise be discharged to the CSO system. Even more importantly, this water is captured during rain events when the system is most vulnerable to sewer surcharges.

It’s clear that the vacuum system is largely responsible for the high BREEAM assessment. Rainwater capture is useful but because it relies on rainfall it’s unreliable. Also, the roof area of high-rise buildings is relatively small, limiting how much rain can be captured.

Here are some more examples where vacuum systems operate successfully:

  • Belfast City Hospital, Northern Ireland 1993: vacuum system installed while hospital in operation
  • Uninove University Sa?o Paulo Brazil 2007: Eight levels for 22,000 occupants; Vacuum system added in late construction phase
  • Hotel Ilva Aasenin, Ørsta,Norway Conferences and 75 hotel rooms 2008: Vacuum system Installed on five levels while hotel in operation
  • WTorre Sa?o Paulo Brazil Hotel and Office towers 2017: 65 levels for 5,000 occupants

Vacuum toilets are nothing new

Vacuum systems were first designed for marine vessels. Every major cruise ship and naval defence vessel is fitted with a robust vacuum system for its low water use, reliability and low maintenance.

The system was adapted for use in multi-storey buildings more than two decades ago.

Energy savings and other benefits

The water/energy relationship is interdependent in high-rise buildings. Unlike vacuum toilets, traditional gravity toilets require water to be pumped continually to all levels.

But the vacuum system interfaces directly with the main sewer network, so there are no holding tanks. The low embodied energy of the system further reduces costs, contributing significantly to a return on investment.

Furthermore, installation costs are 30 per cent less compared to gravity flush toilets, with fewer components and less time and labour. There are also no water leaks with vacuum toilets, and retrofitting existing buildings with the technology is straightforward.

Marion de Courcay in an independent ESD consultant and founder of Pitchpower. She’s an expert in the LeanWater approach to building water performance in multi-storey and high-rise buildings.


Spinifex is an opinion column open to all our readers. We require 700+ words on issues related to sustainability especially in the built environment and in business. For a more detailed brief please send an email to editorial@thefifthestate.com.au

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Comments

4 Responses to “How to slash water use in high-rise buildings by 80 per cent”

  • Marion de Courcay says:

    Katherine, the results at Bloomberg’s London HQ followed Melbourne Water head office are proof that you were ahead of the curve!

  • Frank says:

    0.5 litre per flush – really ? I would be surprised – and doubt that’s the American Standard flush you see in the USA.

    ‘US standards for new toilets
    Pre-1994 residential and pre-1997 commercial flush toilets in the United States typically used 3.4 US gallons (13 L) of water per flush (gpf or lpf). The United States Congress passed the Energy Policy Act of 1992, which mandated that from 1994 common flush toilets use only 1.6 US gallons (6.1 L).

    In response to the Act, manufacturers produced low-flow toilets, which many consumers did not like because they often required more than one flush to remove solids. People unhappy with the reduced performance of the low-flow toilets resorted to driving across the border to Canada or Mexico, or buying salvaged toilets from older buildings.

    Manufacturers responded to consumers’ complaints by improving the toilets. The improved products are generally identified as high efficiency toilets or HETs. HETs possess an effective flush volume of 1.3 US gallons (4.9 L) or less’ – https://en.wikipedia.org/wiki/Flush_toilet

    I have previously read up on the pros and cons of the Australian standard dump flush vs. the US standard vacuum flush.

    If I recall – the benefits of dump flush was it tends to clog less, but typically needs a brush after a ‘dump’ to remove skid marks.

    Conversely vacuum flush typically doesn’t leave skid marks, but clogs more often due to the low flow rate – not an attractive job to clear those pipes.

    This article suggests a vacuum flush using 0.5 litres of water – lemme guess – clog city !

    Hey that should be plenty of work for high-rise plumbers …

  • Andre says:

    Considering Represent no more than around 10% of the water used in residential or commercial buildings in Australia, the authors have made some rather outrageous claims for this market. And still no word of the energy requirements of these systems.

  • Kat Lucas-Healey says:

    Good to see this, Marion! I got laughed at for suggesting vacuum toilets when I was an ESD engineer not so many years ago.

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