If you're planning a new build in Wales, you'll encounter sustainable drainage requirements at the planning stage. This article explains what SABS means in plain terms, why it was introduced, how it affects your project, and what good drainage design looks like on a typical residential site.
What Is SABS?
SABS stands for Statutory Approving Body for Sustainable Drainage Systems. In Wales, Schedule 3 of the Flood and Water Management Act 2010 came into force in January 2019, making Sustainable Drainage Systems (SuDS) a statutory requirement for most new developments.
Unlike England — where SuDS requirements are largely advisory — in Wales they are a legal requirement. You cannot get full planning permission for most new builds in Wales without an approved SuDS scheme.
The approving body is your Local Lead Flood Authority (LLFA), which is your local county council. They must approve your drainage design before construction can start and carry out inspections during the build.
Why Was It Introduced?
Wales has significant flood risk, particularly in the South Wales valleys where urbanisation, steep topography, and high rainfall combine to make surface water flooding a serious problem.
Traditional drainage — which channels rainwater straight into combined sewers or watercourses — increases peak flow rates during heavy rain and contributes to flooding downstream. SABS requires new developments to slow water down, clean it naturally, and release it gradually.
What Does SABS Mean for Your New Build?
For any new development in Wales that drains to a public sewer, SABS means:
1. SuDS are required
Surface water from your development must be managed sustainably. Connecting everything to the nearest combined sewer is no longer acceptable.
2. The hierarchy of drainage options applies
Welsh Government guidance sets out a preference order:
- Store water and use it (rainwater harvesting)
- Infiltrate into the ground (soakaways, permeable paving)
- Attenuate and discharge slowly to watercourse
- Attenuate and discharge slowly to sewer
You start at the top of the list and only move down if the option above isn't viable for your site.
3. You need a drainage approval before construction
Your drainage design must be submitted to and approved by the LLFA before construction begins. This is separate from standard planning permission.
4. Inspections happen during construction
The LLFA will inspect drainage elements during the build to confirm they match the approved design. This is similar to building control inspections.
5. Adoption may apply
If your development has communal SuDS components, the local authority may adopt them for long-term maintenance. This affects design requirements.
What Does a SABS-Compliant Drainage Scheme Look Like?
Every site is different, but typical residential SuDS features include:
Soakaways
Where ground conditions allow, soakaways are often the preferred solution — they infiltrate surface water directly into the soil. Ground permeability testing (a soakage test) is required to confirm feasibility.
Permeable paving
Driveways, paths, and parking areas built using permeable block paving or gravel allow water to filter through rather than run off the surface. This reduces surface water volumes at source.
Rainwater harvesting
Collecting roof water in a tank for toilet flushing or garden watering satisfies the top of the drainage hierarchy and reduces the burden on the drainage system.
Attenuation tanks or crates
Where infiltration isn't possible, water is stored in tanks or geocellular crates underground and released at a controlled rate — mimicking the natural drainage of the undeveloped site.
Filter drains and swales
Vegetated drainage channels (swales) or gravel-filled trenches (filter drains) slow and clean water before it enters the drainage system.
Green roofs
On some buildings, a green roof layer absorbs rainfall and releases it slowly, reducing peak discharge.
Common Misconceptions
"I'll sort drainage out after planning"
Not in Wales. The drainage approval (SABS approval) must be obtained before construction of the drainage system begins. Leaving it late risks delays, redesigns, and potentially enforcement action.
"The building regs drainage design is the same thing"
No. Building regulations cover foul drainage (sewage). SABS covers surface water (rainwater). You need both.
"My drainage engineer will handle it"
A drainage engineer designs the scheme. Your groundworks contractor builds it. You need a contractor who understands what they're building, can sequence it correctly, and can provide evidence of construction to the LLFA. This is where experience matters.
"Soakaways always work"
Only if the ground permeability is sufficient. Clay-heavy ground — common across South Wales — often cannot drain water fast enough for a soakaway to be the primary solution. A permeability test is essential before committing to this approach.
SABS and Groundworks — Why Experience Matters
Getting SABS drainage wrong on a new build is expensive. Common problems include:
- Soakaways in the wrong location (too close to foundations or boundaries)
- Inadequate attenuation volume
- Pipe inverts installed at wrong levels, meaning the system doesn't drain correctly
- Permeable paving installed on top of compacted sub-base that prevents infiltration
- No inspection records, causing issues at sign-off
At Jac Jones Construction, we've been working to SABS requirements since they were introduced in 2019. We carry out continuous training on drainage legislation, work with drainage engineers throughout design and construction, and coordinate with LLFA inspectors at every required stage.
When we quote for groundworks on a new build, drainage is always included as a fully specified element — not an afterthought.
Questions to Ask Your Groundworks Contractor About Drainage
- Have you worked to SABS requirements before?
- Do you coordinate with the LLFA during construction?
- How do you record drainage construction for sign-off purposes?
- Can you advise on soakage testing and infiltration feasibility?
- Do you carry out permeability testing in-house or subcontract it?
Get Drainage Right from the Start
If you're planning a new build in Wales and want to make sure your drainage is designed and built correctly, talk to us early. We're based in Blackwood and cover South Wales.
Call 07446 832296 or send us your project details.
Published by Jac Jones Construction Limited — groundworks and new build contractors in South Wales since 2013. FMB accredited | TrustMark registered | £10m public liability and £5m employers' liability insurance.