The Sustainable Water Industry Group heard how the Flood and Water Management Act of 2010 laid down rules on ease of inspection and upkeep of systems, many of which were underground and hard to monitor.
Terry Nash, director of the UK Rainwater Harvesting Association, told the From Drought to Deluge conference that sustainable urban draining systems (SUDS) heavily based on landscape and plants were a top option.
"In the past SUDS have been heavily defined by attenuation craters underground and nobody knows what happens in terms of silt build up and maintenance," he told delegates at the University College, London venue.
"The act requires systems to be able to be inspected and maintained and this is where water gardens (that use landscape to soak up surface water instead of channels to divert it to ponds or tanks) come into their own; it only takes a scraper to clear up."
Nash said the rainwater harvesting sector had mushroomed in a decade, from a total turnover of around £500,000 in 2002 to around £20m now. Some 6,000 harvesting systems had been installed in homes in the UK in the last year.
However the sector was still dwarfed by other nations such as Germany, which installed 65,000 systems in the last year, and had "flatlined" in recent years because it was so closely linked to construction, also in economic tailspin.
But Gary Grant, who recently published Ecosystem Services Come to Town, said big business was latching on to green infrastructure such as eco roofs and walls. A third of the City of London’s roof tops could be retrofitted to green alternatives.
"A lot of law firms are in competition to have the best green roofs," he said. "Eversheds wanted the most biodiverse green roof in London and now have it. Other law firms are following suit. Pricewaterhouse Coopers just opened their green roof."
Sustainable Water Industry Group director Neal Landsberg called for a "whole-system approach" to water management because "designers do their thing, engineers do their thing and accountants do their thing and they invariable miss stuff".
He added: "We are utterly frustrated at the lack of whole-system thinking and the number of own goals because people haven’t thought enough. If different groups talked to each other they could value engineer problems out."
Watermatic managing director Zac Ribak said his firm was installing systems where loos and washing machines used treated rainwater while bath water and runoff from drives and patios was used to irrigate gardens.