Rainwater Harvesting

Rainwater harvesting systems improve the overall sustainability of a new build project. And we hardly need to point out that this effective and low cost technology is ideally suited to the UK climate.

A typical system will filter and collect rain water in an underground storage tank for:

• Flushing of WCs and urinals
• Washing facilities such as car washes or pressure washers
• Process water requirements such as dust abatement or cooling

Systems are designed to offer a reliable service regardless of weather conditions, and to operate at mains water pressure.

Our design and build service for rain water harvesting systems extends to:

• Roof area, storage tank capacity and water usage design and optimisation calculations
• Detailed system design including integration with building services
• Installation and maintenance

Rainwater harvesting – how it works

This technology uses rain water for specific applications. Most commercial systems do not supply hand washing or drinking water circuits, but they can make considerable savings in WC flushing and other washing and commercial processes.

Water is collected and filtered before being stored in an underground tank. Excess rain water is diverted to the building's rain water drainage system when the tank is full. When water is demanded, a switch senses the water movement (pressure drop) and immediately switches on the pumps. The twin submersible pump-set drives water to the outlet in the same way that mains water is delivered. When the demand ceases, the pumps switch off.

After prolonged periods without rain, a sensor in the tank detects the low water levels. Before the tank is empty a microprocessor controller allows mains water to flow into the tank so it is filled to around 10% of its capacity. This ensures continuing supply while at the same time ensuring that any rain fall can be accommodated in the tank. Rain water systems have proved reliable and effective in operation.

Maintenance requirements are straightforward. They typically involve filter cleaning and periodic hygiene-related checks, plus activities such as removing the accumulation of bio-film (as is the case with mains water storage facilities).