Rainwater harvesting is cost beneficial, Waterwise research finds

The benefits of rainwater harvesting systems outweigh the costs in all instances, whereas the picture is more nuanced with grey water recycling, according to a new report from Ricardo for Waterwise. The research found a number of ways in which rainwater harvesting brings benefits.

Rainwater

It found that rainwater harvesting brought a total net benefit across all collection areas and demand requirements in domestic buildings, and the vast majority of non-domestic buildings which grows as the collection area and demand increases. Where commercial customers pay lower water prices, the savings made from offsetting it with rainwater are lower. The report included a caveat that all building types and sizes have the potential for a private net cost if water demand is low.

When wider social benefits (such as reduced demand on water infrastructure, carbon savings and flood damage reduction) are also considered, the potential benefits over a 20-year system lifetime, according to the research findings, increase substantially.

And rainwater harvesting installations across all building sizes emit less carbon than using mains water over an intallation’s 20-year lifetime.

Grey water

Ricardo found that for the smallest system types, those typically installed in individual houses or potentially for a small block of flats, there was a net private cost for all systems. For larger buildings, including larger blocks of flats, large multi house residential developments or community developments, the water savings exceed the cost of installing the system.

And when net social impact was considered, over a 20-year lifetime, there was, Ricardo reported, a net cost for low- and small-yield buildings, but for all buildings or developments with more than one dwelling, there was a social net benefit.