Rainwater Re-use

Pilot scheme backed by CIRIA where the rainwater from the roof and surface is collected in separate systems and the quality of each source is monitored.   The stored water is used for flushing toilets, urinals and watering soft landscaping.

Roofwater:

Rainwater falling on to the roof is collected via guttering into down pipes which link into a collection chamber and underground tanks constructed from ‘plastic’ modular units (below left), wrapped in geotextile protection fleece and surrounded by a suitable membrane.   The water enters the building via a pump to a header tank situated in the building roof.

Surfacewater:

Rainwater falling on to the car park area drains through porous block paving (above right) into a retention zone below.   The retention zone consists of no-fines granular subbase placed within a robust weldable membrane.   The collected water enters the building via a pump to a header tank situated in the building roof.

Control Philosophy

The pumps for the system are controlled via a bespoke programmable logic control (PLC) situated inside the building (above right).   The PLC manages the phasing of the pumps for the rainwater storage areas and if it is necessary to top the system via the mains supply.  The primary source of water is from the roof area storage tanks. When the volume of available water, falls below a certain level, the pump drawing water from the retention zone takes over.   If the water demand should deplete the supply from here, this is registered on the internal control panel and mains water is allowed to fill the header tank for the interim period until the primary and secondary storage areas are recharged during a period of rainfall.