Surface Water Drainage in Scotland: What Developers Need to Know
Scottish Water requires developers to follow a five-tier drainage hierarchy before connecting to the public sewer network, with robust evidence needed to justify lower-tier options.
During Scottish development projects, managing surface water drainage — the runoff from roofs, paved surfaces, and other impermeable areas — requires careful planning regarding disposal methods and discharge locations.
Many urban developments initially consider discharging surface water into the public sewer network. However, Scottish Water approval is mandatory and only granted after alternative options have been thoroughly assessed and found unfeasible.
Scottish Water’s Drainage Hierarchy
Current Scottish regulations require developers to follow a five-tier hierarchy of disposal methods, ranked from most to least sustainable:
- Rainwater reuse (harvesting systems, water butts)
- Infiltration (soakaways draining into soil)
- Discharge to water bodies (watercourse, canal, loch, or SuDS)
- Discharge to surface water sewer
- Discharge to combined sewer
Developers can only pursue options 4 and 5 after providing “robust evidence — both technical and non-technical — justifying why higher-ranking options in the hierarchy are not feasible.”
Key Takeaway
Failure to implement compliant drainage strategies early can result in project delays, increased costs, or sewer connection denial. Early engagement with drainage specialists ensures the correct hierarchy is followed and supporting evidence is compiled for successful Scottish Water applications.