The Standards are built on 11 principles grouped under natural management, integrated design and planning links.  

Principle 1, the natural approach, explicitly directs designers to “mimic natural drainage” by managing runoff at or near the surface and close to its source. This means on-site rainwater reuse is priority 1: Standard 1 states that runoff “shall be collected for non-potable use” wherever practicable. In other words, rainwater harvesting is top of the hierarchy. Standard 1 also lists infiltration and discharge to surface waters as second and third priorities. Any lower-priority discharge (e.g. to sewers) must be justified by showing that higher priorities have been maximised. The Standards highlight the value of rainfall as a resource.  

Principle 3 defines the SuDS Approach as one that “recognises the value of rainfall and runoff as a resource”. Standard 1 reinforces this with requirements on rainwater harvesting: schemes should include rainwater capture whenever there is a non-potable demand, irrigation need or water-stressed location. (Indeed, the guidance notes that many parts of England face serious water stress, making onsite reuse ever more critical large-event harvesting systems must be designed to the industry standard BS EN 16941 and demonstrated with appropriate rainfall data. In practical terms, this means tanks, filters and controls should be sized and tested, not just ad-hoc garden barrels. The emphasis on reuse and infiltration reflects the Standards’ goal of reducing reliance on drainage networks and preserving water in the local environment. 

How do small-scale features like water butts and rainplanters fit into this?  

The guidance does not ban them, but it sets conditions. Standard 2 requires that everyday rainfall (typically the first 5 mm) is intercepted on-site so it doesn’t run off. Common SuDS like green roofs, permeable pavements, swales and basins are listed as acceptable interception methods. Rainwater harvesting tanks also qualify but simple garden water butts do not count automatically. In fact, the guidance warns that “water butts... limited to garden use during dry periods” are not considered compliant with Standard 2 unless specifically designed and justified. In plain English: a scatter of garden water butts is unlikely to meet the new 5 mm rule unless you demonstrate by calculation that they actually capture, hold that runoff and allow for more storage. This is why we slow release rainwater harvesting devices are so useful so that there is always excess capacity ready for a specific rainfall event. We follow this up with monitoring to validate our water attenuation. 

The Standards make it clear that where you put SuDS is as important as what you put. Simply adding measures at random will not satisfy the requirements. Strategic modelling shows the payoff of the “right place, right solution” approach. For example, Thames Water’s stormwater plan reports that by using hydraulic models to target interventions, just 5% of the most effective locations delivered 65% of the total flood reduction benefit, and the top 30% of sites yielded nearly 90% of the benefit. In other words, a few well-placed planters or ponds can outperform many poorly sited ones.  

In practice this means deploying data and models to guide choices: for instance, determining whether a green roof or a chain of storage planters is more effective at a particular site; or mapping where swales will capture flows to meet demands. Catchment models help councils and developers see cumulative impacts ensuring that multiple schemes in one area will still meet overall runoff targets. By contrast, without modelling one risks complying in theory but failing in practice. The “right solution” for a riverside site might be a wetland basin, while a city street might need permeable paving and planters. Optimisation modelling identifies these optimal combinations, making sure that for every 5 mm storm Standard 2 is met and every 1% storm Standard 3 is satisfied exactly where it matters most.