How to make the best use of household waste water. Frequently asked questions about greywater recycling are answered here.
What is Greywater?
Wastewater from all sources in a property other than toilets is known as greywater.
Most greywater recycling systems collect and treat wastewater from showers, baths and wash basins, excluding the more contaminated water from washing machines, kitchen sinks and dishwashers. Greywater recycling systems collect this water, treat it and re-use it for purposes that do not require drinking water quality. This recycled water can be used to flush toilets, water gardens and sometimes feed washing machines.
Greywater recycling systems can be installed in new or existing buildings and have the potential to meet a significant proportion of domestic demand for water.
For more information see our document:
Is it for me?
Before installing a greywater recycling system you should:
- compare how much greywater you are likely to generate (which will depend on the number of baths and showers taken) with your demand for reclaimed water (which will depend on the number of toilet flushes or volume required for the garden);
- consider the potential savings from reduced water consumption against the costs of installation and maintenance.
Systems installed in larger buildings tend to be more efficient than those installed in individual properties, as bigger systems can use more sophisticated treatment and can be maintained centrally.
How does it work?
A typical greywater system collects wastewater from baths, showers and washbasins. The water is then treated and pumped to a tank for storage until it is required for toilet flushing or garden watering.
The method and standard of treatment in a greywater system generally varies with the size of the system. Larger greywater systems that supply more than one property tend to use more sophisticated treatment methods than smaller, individual systems. Treatment can be classified as 'physical' or 'biological'. 'Physical' treatment is common in small-scale systems and usually consists of a basic filtration process. Biological treatment is generally used in larger systems and works in a similar way to the processes used at a sewage treatment works. Some systems use a combination of the two methods, giving a 'bio-mechanical' process.
Basic physical systems tend to require the use of chemicals similar to bleach to stop the growth of bacteria while the water is in storage. Care must be taken to ensure no cross connection with mains water occurs. Further guidance is available at the Water Regulations Advisory Scheme (WRAS) website. (Click on link in right hand column)
Will it save me money?
Greywater recycling has the potential to save a third of domestic mains water usage.
If your property is metered, this will reduce your water bill. Your financial savings will depend both on the price of water in your area and the volume of water re-used.
Greywater systems are relatively expensive; therefore it may be some time before the system pays for itself financially. Studies have shown that payback periods for simple, domestic systems can be longer than the life of the system.
How much will it cost?
Installing a system for use in an individual property can be expensive. A typical, off the shelf, single house, domestic system may cost in excess of £3,000 to purchase. This system will also incur running costs and installation costs. Systems that are installed in new buildings are usually more cost effective than those retrofitted into existing properties; communal systems are more cost effective than those installed in single properties.
Will it benefit the environment?
The potential water savings from widespread greywater reclamation are huge. A well specified, correctly installed, fully operational and well-maintained greywater system could save one third of the water taken from the mains supply by a domestic property. If widespread, this would reduce both the pressure on water resources and the quantity of sewage requiring treatment.
While greywater systems save water, they also use energy. This works against some of the environmental benefits gained from saving water. Cheaper and less energy-intensive ways of saving water include low-flush toilets, low flow taps, low flow showers and waterless urinals.
What do I do now?
There are easier ways to save water. Our publication Conserving water in buildings gives a summary of the many ways we can all save water, including greywater reclamation.
If you have any specific questions about greywater reclamation e-mail us at enquiries@environment-agency.gov.uk
