Water systems

Rainwater harvesting

Rainwater harvesting is the collection of rainwater falling on and around a development that might otherwise have been diverted to sewers or the ground.

The basic principle is to capture this water and use it instead of mains water, where drinking water is not required. Rainwater harvesting can reduce flood risk during heavy rainfall, it can also reduce carbon emissions.

Energy is saved by not using highly processed tap water to flush toilets, irrigate plants, wash cars and run washing machines.

The harvesting process collects water from the roof into a tank. The most basic system is where water is collected in a water butt connected to rainwater downpipes.

A more sophisticated system that results in a better quality water supply is to use an above or below-ground sealed tank, which may need to have an automatic main–water top-up facility and a filter.

The tank size needs to take into account the roof area and likely usage. Commercial systems are likely to need larger storage tanks to match the harvesting potential of many commercial roofs and the high demand for non–drinking water. Some rainwater tanks can be built into foundations.

A rainwater harvesting feasibility study should be carried out by a specialist and submitted with the planning application.

Significant water savings can be made by fitting water-saving taps and shower fittings, and by using energy-saving white goods and installing flow reducers.

More information on this can be seen on the water resource planning page.

Grey water recycling

Grey water is water from basins, showers, baths and washing machines. If sufficient roof space is not available to harvest rainwater, as may be the case in multi-storey urban developments, grey water treatment machines can be installed.

The grey water machines clean water from baths, showers, basins and washing machines to a level suitable for toilet flushing. This recycled water excludes water from kitchen sinks due to fats, grease and oils.

This is worthwhile to save water especially as a large percentage used in domestic homes is for toilet flushing. However, these machines use electrical power to run and the impact of this should be considered in the overall energy performance of the development.

Grey water can be used more simply for watering the garden, collected by using simple diversion kits that enable you to channel grey water from your downpipes into the garden.

A grey water recycling feasibility study should be carried out by a specialist and submitted with the planning application.

If grey water recycling is not feasible, rainwater harvesting should be considered in this feasibility study.

Significant water savings can be made by fitting water-saving taps and shower fittings and by using energy-saving white goods and installing flow reducers.

More information on this can be seen on our water resource planning web page.

Relevant policies

Brighton & Hove Local Plan: