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Millenium Green comprises 24 houses and an office incorporating various water efficiency and other environmental measures. It was developed by Gusto Homes, a small housebuilding company committed to incorporating environmental good practice and sustainable development objectives into housing projects.


All houses are fitted with a rainwater harvesting system, developed by Gusto Homes and Freerain, the system specialists. Severn Trent Water and the Environment Agency undertook a 12 month monitoring study.

The rainwater system uses underground storage tanks big enough to provide nonpotable water to the home for 18 days. If the supply of rainwater becomes low, the tank is automatically topped up by the mains supply. Homeowners can see if their tank is being fed by the mains supply by a light in the control box.

The harvested water is used for toilet flushing, washing machines and gardening. Using rainwater in washing machines has the added advantage of reducing the amount of detergent required as it is softer than mains water. An additional benefit is that there is no storm water run-off into local drains. When the tank is full, any excess overspills to a soakaway.

The cost of a complete system is approximately £1000 for a 3.3m3 tank and £1500 for a 6.5m3 tank. The payback period can be 20 years, therefore the systems are not currently viable from a purely economic viewpoint. 

Gusto Homes has also developed a system that integrates rainwater harvesting with sustainable urban drainage. This system allows any overflow from the rainwater tank to feed into an attenuation tank from which water can be released either through a permeable membrane to land or into the stormwater drain. The Millennium Green rainwater harvesting system won Gusto homes an Environment Agency 2003 Water Efficiency Award.

Project team

Gusto Construction Environment Agency Severn Trent Water Ltd

Further information

G usto Construction