Fortunately, we in the UK are subject to light regulation when it comes to harvesting our plentiful rainfall. This is in contrast with countries such as the USA where legislation sometimes seems to vary at county level. However, how that water is utilised and piped into buildings is sensibly regulated. This is to avoid any health hazards that untreated rainwater might present and to ensure it is never confused with drinking water from the public mains supply.
What Regulations Govern UK Rainwater Harvesting?
The main regulations and guidelines come from these sources:
- BS EN 16941-1:2018 (this supersedes BS 8515:2009)
- Water Regulations Advisory Scheme (WRAS)
- BRE Environmental Assessment Method (BREEAM)
In this article, we have selected these quick tips that reflect the main thrust of the regulations:
1) Prevent Backflow Into The Mains Supply
The primary thrust of the WRAS guidelines is to make it practically impossible for non-potable water to contaminate the public mains water supply, whether outside or inside the property. To the extent that any possible pathway for germs or pathogens is not permitted. This includes motorised valves, check valves and non-return valves where organisms could infiltrate through the device from non-potable water. A physical air gap is the only permitted mechanism, and must be included in your design in order to obtain planning approval.
2) Label Your Pipes And Appliances
Harvested rainwater water must be clearly labelled as non-potable or “non-wholesome” – in other words, not suitable as drinking water. Non-potable pipework, whether underground or inside the property must be visibly identified. Appliances, outlets and valves should be tagged or labelled in line with WRAS Guideline IGN 9-02-5. Two simple examples would be: labelling inside the cistern lid of a toilet that is flushed using rainwater or labelling the back of a washing machine.
3) Commission The System Professionally
Know the other regulations that apply when connecting a rainwater harvesting system to a building’s plumbing. BS 6700 states that drinking and non-potable water systems must be isolated from each other. All pipes and fittings are subject to BS 6700:2006, 18.104.22.168. The electrics are governed by BS 7671. The system must be properly flushed through and tested during commissioning, which may be performed only by professionals plumbers approved by WRAS. Further information on this can be found in the WRAS Advisory Leaflet No. 9-05-01.
4) Storage Tanks Need A Well Designed Overflow Capability
Overflow that has not been planned for can damage the surrounding infrastructure and even cross-contaminate drinking water supplies in extreme cases. The overflow of any tank within a building must have a capacity greater than the inlet so that in times of heavy rainfall, excess water will easily be carried away. It must also prevent backflow and the ingress of vermin.
Choose The Right Rain Harvesting System For Your Project
Download the Rainwater Harvesting Systems guide: Everything you need to know about choosing a rainwater harvesting system as a first step toward arming yourself with knowledge about this ever popular technology. When it comes to planning and designing your next project take advantage of our in-depth expertise as the UK’s oldest supplier of systems and contact us for an initial consultation regarding your requirements.