The sky's the limit
Rainwater harvesting is at the forefront of the sustainability debate. Dean Stiles reports on what is said to be a market which is doubling every year for domestic and commercial uses
He says: "The UK market is relatively small compared to continental leaders Germany, who have been at this for a lot longer than the UK. But the UK market is broadly doubling year-on-year, not only for domestic but for commercial systems as well."
Rainwater, considered a problem because it can cause flooding, can be an asset if stored for non-potable use. There are many applications where it can substitute mains water for cleaning, cooling, irrigation, humidification, fire fighting, and toilet flushing. And there are a variety of systems on the market.
The general concept is the same with water first filtered then stored for pumping directly to the points of use or to an internal break-tank. If the system runs low on rainwater, a mains water back-up unit provides continuity of supply.
The government's housing development plans for an already water-constrained South-east, coupled with policies designed to achieve sustainable communities, is highlighting the use of harvested rainwater to reduce demand on mains water, to help stormwater management, and to save on the energy used in producing potable water.
"Commercial business has been growing at a steady rate. But we now are seeing the impact of last year's hose pipe bans, which have brought rainwater harvesting to the attention to the householder," says Fox.
But retro-fitting a rainwater harvesting system in domestic property other than for gardening water is not financially viable. "If you're looking at supplying toilets and washing machines, then it's cost prohibitive," says Fox.
Rainwater harvesting is primarily a new-build market. "Certainly there is a lot of activity in schools, and most new-build schools are considering various environmental technologies. Whether they ever get through the budget is another matter. We do a lot of work on the design side of it but many projects drop out quite early on," he says.
Last year, the company completed one of the largest housing installations in the UK with 120 underground tanks designed to help a new housing development for Cornhill Estates and Miller Homes at Upton, Northampton. This will enable the development as a whole to reduce its consumption of mains-water by around 40%, compared with equivalent developments.
The rainwater retained on-site in the storage tanks helps to reduce demands on the overall stormwater management system, thus also playing a part in reducing flood risks - a key requirement on this site.
In January, Polypipe Civils, UK manufacturer of drainage, sewerage and stormwater management solutions, signed an agreement with the Ministry of Defence (MoD) to provide 150 of its Eco-Vat rainwater harvesting tanks in the largest rainwater harvesting contract ever agreed in the UK.
Polypipe Civils will supply the tanks to main contractor Aspire Defence over seven years. The first three tanks, with a combined capacity of more than 42,000 litres, are due to be installed on a MoD site in Tidworth, Wiltshire, as part of the redevelopment of living quarters in conjunction with subcontractor Dean and Dyball.
On the Tidworth site, the Eco-Vat tanks will be used as a cost-effective, stand-alone, solution for rainwater harvesting.
As rainwater collects on the roofs of the dwellings, it will go through an individual treatment system before being filtered into the storage tanks. This water will then be reused for toilet flushing by residents on-site.
Rachel Roberts, marketing manager for Polypipe Civils, says: "Rainwater harvesting is at the forefront of the debate surrounding environmental and sustainability issues, even more so with the water shortages seen across much of England."
Planning requirements usually drives specification of rainwater harvesting. "It is partly to do with sustainable drainage," says Fox, "and the fact that a lot of the prime building land has gone so builders often struggling with more difficult land."
On larger commercial installations, it is possible for users to make a financial saving on water costs despite the relatively low price of potable water in the UK. Interest in rainwater harvesting has also increased with its inclusion in 2004 in the Government Water Technology List.
Businesses investing in the products on the list can claim tax relief on both the capital and installation costs, offsetting 100% of the cost and installation in the first year.
Fox does not expect any legislative changes that will drive the adoption of rainwater harvesting use in the UK. And without compulsion in the form of building regulation changes, the UK's low water prices are likely to limit growth in rainwater harvesting despite the relatively low cost of installations.
Commercial installations start at £5,500 supplied, with as much again for installation. "We are looking at a large superstore at the moment, which is coming in at £20,000. We are dealing with low water tariffs, so you need a big roof, big tanks and big water usage to make any paybacks," says Fox.
This is especially evident in the agricultural sector, which is very cost sensitive. "Farm buildings are very tolerant to DIY installations. We get a lot of requests. But it's a knowledge exercise, and they usually source some cheap tanks and do it themselves," he says.
The economy of a system depends on various factors. Charges for water supply and sewage services vary greatly between the various UK supply companies, and these charges can significantly affect the potential savings of any system. Frequently, there is also a stormwater charge that should also be considered.
The capital cost of the installed system is affected by several factors, including the equipment used and the ground conditions on site.
Ongoing costs that should also be taken into consideration are the energy cost of running pumps and cleaning and maintenance costs.
All these are fairly unique for any commercial water consumer. So, it is not possible to make generalised claims about cost effectiveness or paybacks that can be between three and 30 years, says Fox.
Planning requirements are equally as variable with no clear guidance at regional level. Some areas push for water harvesting, while others are seemingly ignorant. But, with water costs likely to rise steadily, rainwater harvesting will become more common, even when not demanded for stormwater management.