Flushed with pride – Water saving toilets

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Beth Askham takes us on a tour of some water saving loos.

Toilets can flush away litre upon litre of potable water, with up to 25% of our home’s water going down the toilet.* It used to be worse; before 1982 when dual-flush toilets were introduced, toilets in Australia had an average flush volume of 11 litres. Now, the most efficient toilets use around 3.3 L per flush and to use less water than this we might need to radically change toilet design. New water-saving toilet designs in the pipeline incorporate air assistance, vacuum piping or urine separation.

How low can we flow?

Dual flushing is the standard for water-efficient toilets in Australia. The most efficient dual-flush toilets use 4.5 L for a full flush and 3 L for a half flush, with an average flush volume of 3.3 L. These toilets are rated as 4 stars under the WELS rating scheme (the more stars, the more efficient the model). Some models with an integrated hand basin that flush with greywater reach 5 stars, but there are no 6 star toilets available at this stage.

Indeed, we may be at the limit of the minimum amount of water used for flushing. Too little water in a flush can create drainage problems as it’s the water that pushes the waste along sewer drainage lines. Ways to get around drainage issues and still reduce the amount of potable water used includes flushing with greywater, using a Drainwave that releases water from your house in stored batches (see www.drainwave.com.au) or using another type of toilet that doesn’t depend on water–such as those that use air pressure to flush or composting toilets.

Urine separation toilets

Urine separation toilets reduce the amount of flushing required. They are more common in Europe but there are some examples of their use in Australia. The University of Technology Sydney (UTS) Institute for Sustainable Futures is working to divert urine from their sewerage system by installing dual plumbing at its Barangaroo development and in their new UTS Broadway building in Sydney. They plan to reuse the urine’s nutrients as agricultural fertiliser. “It could easily be argued that ‘taking a leak’ is our most apt description for going to the toilet as it literally involves leaking valuable resources into the waste stream,” says Professor Cynthia Mitchell, who is leading the project.

Vacuum toilets

Vacuum toilets are increasingly being used in offices, public buildings and portable toilets, but it’s still early days for them in residential dwellings. Vacuum toilets use less than one litre each flush and it’s only to wash the pan. They essentially use atmospheric pressure to push waste into toilet piping that’s kept at a lower pressure.

Pumps keep the piping network at a 55% vacuum and when a toilet is flushed, this drops to 35% before it builds back up. All waste is macerated and then sent to the sewer, avoiding any drainage issues. An advantage of vacuum toilets is that you can place them anywhere in the building layout without needing to account for gravity-fed piping, as the vacuum piping can remove waste vertically if needed. Managing Director John Neskudla of Vacuum Toilets Australia says, “Vacuum toilets are the future; we cannot continue to flush our most precious resource down the toilet.”

Read the full article in ReNew 125