Is it legal to collect and use rainwater in the UK? The answer may not seem entirely obvious when we look at examples from elsewhere in the world.
In the American state of Colorado, for instance, rainwater collection has historically been restricted because of the water-rights system used across the arid western states. These laws date back around 150 years, when access to land, mineral claims and water was often governed on a first-come, first-served basis.
Under this system, a homeowner was not necessarily considered to own the rainwater falling on their property. Instead, the water was expected to flow into rivers or groundwater supplies belonging to established water-rights holders.
This may seem unusual to those of us living in the comparatively damp UK. However, the restrictions are rooted in the history of water scarcity and ownership in the western United States. Stories have even circulated about people being prosecuted for collecting rainwater from their own roofs.
Is It Legal to Collect Rainwater in the UK?
Yes. Collecting and using rainwater is legal in the UK.
Rainwater harvesting is also encouraged by many water companies, particularly in the drier south-eastern parts of the country, where rainfall is generally lower than on the west coast.
There is nothing to prevent a householder from collecting rainwater for uses such as:
- Garden watering
- Toilet flushing
- Washing clothes
- Vehicle washing
- General outdoor cleaning
However, standards and regulations apply when rainwater harvesting systems are connected to a building’s plumbing, particularly where there is also a connection to the mains water supply.
Regulations also apply where harvested rainwater is intended for drinking, bathing or other uses that require a higher standard of water quality.
What Regulations Apply to Rainwater Harvesting?
Developers, project managers, installers and property owners should be familiar with the main regulations and guidance affecting rainwater harvesting systems.
Water Regulations and WRAS Guidance
The Water Regulations Advisory Scheme, commonly known as WRAS, provides guidance covering mains water supplies and the valves, fittings and appliances connected to them.
One of the most important considerations is backflow prevention.
Where a mains water supply is used as a backup for a rainwater harvesting system, there must be a suitable physical air gap. This prevents non-potable rainwater from being siphoned or forced back into the mains drinking-water supply.
Relevant legislation includes:
- The Water Supply (Water Fittings) Regulations 1999 for England and Wales
- Separate water fittings legislation for Scotland
- Separate water fittings legislation for Northern Ireland
The official WRAS guidance should be consulted when designing or installing any system that interacts with the mains supply.
BS 8515: Rainwater Harvesting Systems
BS 8515 provides a code of practice for rainwater harvesting systems.
It covers areas including:
- System design
- Risk management
- Water quality
- Installation standards
- Commissioning and testing
- Inspection and maintenance
The purpose of the standard is to encourage consistent, safe and reliable rainwater harvesting installations.
Planning Permission
Rainwater harvesting systems are generally covered by permitted development rights because they are considered a form of rainwater recycling.
Planning permission is therefore not usually required for a standard installation.
However, it is sensible to check with the relevant local planning authority, particularly where:
- The property is listed
- The site is within a conservation area
- A large above-ground tank is proposed
- Significant excavation or structural work is required
Including rainwater harvesting within plans for a new building may also support the environmental and sustainability aspects of a planning application.
Identifying Rainwater Pipes and Outlets
Harvested rainwater is normally classed as non-potable or non-wholesome water, meaning it is not suitable for drinking unless it has received appropriate treatment and testing.
Pipes carrying harvested rainwater should be clearly identified. This applies to pipework installed both below ground and inside the property.
Valves, taps, appliances and other outlets should also be labelled where appropriate.
Examples include labels:
- On rainwater-supplied outdoor taps
- Inside WC cistern lids
- Behind washing machines
- On valves and access points
- On rainwater distribution pipework
Labelling helps prevent harvested rainwater from being confused with mains drinking water during maintenance, alterations or future plumbing work.
BREEAM Assessments
The Building Research Establishment Environmental Assessment Method, or BREEAM, is not itself a legal requirement.
It is a widely recognised environmental assessment method used for commercial buildings and larger development projects.
Installing a rainwater harvesting system may contribute towards a building’s BREEAM performance by reducing its demand for mains water and improving its overall environmental credentials.
Drinking and Higher-Quality Uses
Rainwater collected from a roof is not automatically suitable for drinking.
Where harvested water is intended for drinking, bathing or other sensitive uses, a suitable treatment system will normally be required. Depending on the application, this may include:
- Fine particulate filtration
- Carbon filtration
- Ultraviolet disinfection
- Water-quality monitoring
- Laboratory testing
The treatment system must be designed around the intended use of the water and the likely sources of contamination.
Keep Up to Date with Regulations
The requirements described above represent the principal regulations and guidance applying to rainwater harvesting systems.
However, standards and legislation can change. Property owners, installers and employers should always confirm that they are working to the latest requirements before specifying, installing or modifying a system.
Find Out More
Rainharvesting Systems can provide advice on the design, installation and regulatory requirements of domestic and commercial rainwater harvesting systems.
To discuss your project, call 01452 772000 or email sales@rhsl.co.uk.