In July 2025, the UK Government published its latest vision for sustainable drainage systems (SuDS) on new developments. For the first time, water reuse takes centre stage, highlighting the critical role rainwater harvesting will play in managing rainwater locally.
If you are a civil engineer, design engineer, or consultant, it is vital to understand how these changes will influence your projects. The new standard does not just focus on slowing water down to prevent flooding, it promotes a holistic approach that combines drainage, biodiversity, climate change resilience, and now water supply strategies.
Put simply, rainwater harvesting is no longer just an optional add on. It is becoming a key component of SuDS compliance.
Why the Shift?
Traditional drainage approaches often treated rainfall as a problem, something to be moved away from developments as quickly as possible. The new standard flips this approach. It recognises rainwater as a valuable local resource that should be managed and reused wherever possible.
By collecting rainwater close to where it falls, there are two benefits…
- Flood risk reduction by slowing and storing water to protect downstream systems
- Potable water savings by reusing rainwater for non potable purposes, easing the pressure on mains water supplies
It is a win win approach that delivers resilient communities, greener developments, and more sustainable infrastructure.
Standard Runoff Destinations
The new SuDS guidance introduces a clear hierarchy for how stormwater should be managed on site. At the very top, labelled “priority one”, is collection for non potable reuse.
In practice, this means that rainwater harvesting must now be considered first on new build sites where SuDS requirements apply.
Rainwater harvesting should be applied wherever any of the following conditions are present…
- A clear demand for non potable water, such as toilet flushing, vehicle washing, or process water.
- A need for irrigation of landscapes, including green roofs, living walls, or planted gardens.
- Where developments are located in seriously water stressed regions of the UK.
Further Considerations
To comply with the standard, rainwater harvesting systems must be properly designed and integrated, not treated as a bolt on feature. Key points include…
- Systems should be sized in accordance with BS 16941 1 to ensure compliance and efficiency
- Water butts are not considered a SuDS solution, as they lack the active management technology required. Only properly engineered systems will meet the standard
- Where communal rainwater harvesting is used, such as on residential projects, potential risks to public health must be minimised through design and operation
Our Tips for Successful Integration
With over two decades of experience in designing, installing, and maintaining rainwater harvesting systems, we have seen what works and what does not. Our advice…
- Book onto a CPD with us to gain insight into best practice, system sizing, and the common pitfalls to avoid
- Engage early and involve rainwater harvesting in the initial design stage for maximum efficiency and water savings
- Think long term and ensure systems are easy to maintain, with accessible components that will not cause issues years down the line
The Role of Stormsaver
At Stormsaver, we are strong advocates for rainwater harvesting as the logical solution to managing rainwater locally. Unlike outdated approaches that only focus on holding back water, harvesting allows us to reuse it productively, supporting both resilience to flooding and reduced reliance on potable water infrastructure.
That is why we are actively supporting engineers and designers through our dedicated CPD sessions on rainwater harvesting and Smart Sustainable Urban Drainage compliance.
If you are a civil or design engineer, book your place on our CPD today. Stay ahead of the new national standard, learn how to integrate rainwater harvesting effectively, and make sure your projects are compliant, resilient, and sustainable.
