Water Demand.

Water demand in Europe has increased by over 50% in the last 30 years and is expected to continue in this trend.

In the UK, where the cost of high quality water is still relatively cheap, we are continually using drinking water for a number of industrial and domestic functions which could be replaced by less treated (green) water.

A cartoon of a child being bathed.
Green Roof Water Recycling System (GROW) Test Rig at Cranfield University

Green Roof Water Recycling System (GROW) Test Rig at Cranfield University


Water is gradually becoming a resource requiring ever greater conservation measures to protect. Hence the recycling of relatively clean 'wash water' (grey water) for other, lower grade purposes is important.

The award winning Green Roof Water Recycling System, GROW, developed by WWUK is ideal for new build or refurbishment schemes of low-rise multi-story housing and, therefore, particularly suited to the requirements of Local Authorities, Housing Associations and other high density development where significant numbers of residential units are accommodated in a single block under one roof.

GROW is essentially a tiered garden of low growing, flowering, native plants, whose roots can perform the same cleansing function as a reed bed.

Green Roof Water Recycling System (GROW) Test Rig at Cranfield University

GROW 'exposed' showing troughs, plants and support system.

Grey water (used wash water collected from showers, sinks and baths) is treated as it flows through the plants' root system. The treated water is termed green water, which is safe to use for toilet flushing, cleansing public areas, and watering the garden.

Price can be negotiated, but allow around €120-180 per person (based on 40 people).

GROW 2, (its baby sister) measures about 2m x 1m x 1m (high) and is suitable for installation on individual properties to produce green water for garden watering and simple horticultural irrigation. (Follow this link for more information about GROW 2)

Beat the next drought and hose pipe bans!

Both GROW and GROW 2 are living systems and require care and simple maintenance to function effectively.

Other Advantages of the Green Roof Water Recycling System:

Installed as a single unit at roof top level, this system will require no extra land or valuable basement space, something that makes some other external forms of water recycling a more expensive option, especially in inner cities. The system would also be able to provide thermal insulation to buildings in winter and act as a cooling layer in summer.

In 2002 the DTI awarded GROW a grant under its Partners in Innovation (Pii) scheme to carry out further research using a live source of grey water. GROW was installed at the School of Water Sciences at Cranfield University where it successfully treated the grey water from a block of student flats.

Both GROW & GROW 2 are patented systems.

Grow at the The Office Group

Opening Day for the GROW installation at The Office Group, Gray's Inn Road, London

For more information on Green Roofs see greenroofs.org