The Environment Agency - England and Wales

Plan for less water down drain warns UK environment agency report


Drainage design standards should be reviewed and guidance developed for retrofitting water efficient fixtures and fittings to ensure sewerage systems can work with less water, says the just-released Environment Agency report ‘Less Water To Waste’.

The joint investigation by scientists and water experts examined concerns that increasing water efficiency in the home and office could result in bad smells and flooding from blocked drains and sewers.

Ian Barker,  the Environment Agency’s Head of Water Resources, said: “We expect the widespread introduction of water efficient fixtures and fittings, more conservative water use and extensive metering to lead to a significant fall in the nation’s water demands. The Code for Sustainable Homes - the sustainability rating system for new housing in England - and the regulatory level for water efficiency to be introduced in the Building Regulations next year will also reduce water use in new homes.

“We needed some good quality research into what the impacts of this might be. We were particularly interested in assessing the impact of low-flow toilets because reducing flush volume is the most effective way of cutting demand. But, flushing is vital for shifting sewage through the system.”

The report concludes that higher water efficiency standards are unlikely to pose problems for most drains and sewers. However, reducing toilet flushes to very low volumes could be an issue in a few existing buildings where drains serve a small number of single-occupancy properties.

For new build, the study recommends that drainage design standards are reviewed to accommodate higher levels of water efficiency. Smaller and fewer pipes set at steeper gradients and new innovations such as toilets that use air as well as water during the flush, for instance, would help to avoid blockages in highly water efficient buildings, says the report.

In existing properties, the study concludes that drainage layout needs to be taken into account before deciding whether replacing an old toilet with a new low flush model is viable. It also recommends further research to help find ways to tackle drainage issues in existing buildings in future.

Ian Barker added: “Our towns and cities cannot function without drains and sewers. But as rainfall becomes less predictable as climate change bites, we have to become more efficient with water. Adapting our infrastructure to deal with the knock on effects of that has to be a national priority.

“This study found no reported cases of blockages in existing housing caused by water efficiency measures. But it does show that there needs to be further research.  We look forward to discussing the findings with the Government, water companies and the wider water industry.'

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