Below Ground Drainage Design

Drainage System Design & Installation Services

Effective drainage is fundamental to the success of any development project. Without the right systems in place, sites can experience flooding, structural damage, non-compliance with regulations, and costly future repairs. Our drainage design and installation services ensure every project is delivered to the highest standard of performance, safety, and sustainability.

Compliance with Building Regulations

All new drainage systems, or modifications to existing ones, must comply with Building Regulations, which are reviewed by the local planning department. This applies to both foul water and surface water systems:

Foul water drainage systems: Responsible for wastewater from kitchens, bathrooms, utility rooms, and car washing areas.

Surface water drainage systems: Handle rainwater runoff from roofs, paved areas, and external surfaces.

We ensure that both systems are separated, properly sized, and designed to meet all statutory requirements. By engaging with local planning authorities early in the process, we minimise delays and help projects progress smoothly.

Phases of Drainage System Construction

The installation of a below-ground drainage system involves a structured process. Each stage requires technical expertise and precision to ensure long-term reliability.

1. System Design and Planning

Detailed surveys of existing ground levels, soil conditions, and watercourses.

Hydraulic calculations to estimate flow rates.

Selection of appropriate pipe diameters, gradients, and materials (uPVC, clay, or concrete).

Integration of access points such as manholes, gullies, and inspection chambers.

This planning stage provides the blueprint for a drainage system that is robust, cost-effective, and sustainable.

2. Procurement and Material Management

Selection of high-quality pipes and fittings that meet industry standards.

Coordination of transport and storage to prevent damage before installation.

Proper material management ensures the project runs efficiently and avoids unnecessary delays.

3. Excavation Works

Safe trenching methods with shoring or trench boxes to prevent collapse.

Excavation to exact depths and gradients for correct pipe alignment.

Laying granular bedding to provide a secure foundation.

This stage is carried out with strict safety measures to protect workers and prevent ground instability.

4. Pipe Installation

Pipes are carefully aligned and laid to the correct gradient.

Joints are sealed to prevent leakage and infiltration.

Protective backfill is placed around pipes to absorb pressure from soil movement.

Manholes and inspection chambers are constructed for future access and maintenance.

Pre-backfill testing, including pressure or air tests, confirms the integrity of the system.

Precision at this stage ensures the system performs reliably for decades.

5. Backfilling and Reinstatement

First layer of granular material compacted around the pipe system.

Successive layers of soil reinstated to original levels.

Final surface restoration of roads, pavements, or landscaping.

Attention to detail during reinstatement prevents settlement and ensures the site is left in a finished condition.

6. Final Testing and Commissioning

CCTV inspections and flow tests to verify system efficiency.

Sign-off from building control or local authority.

Connection to sewers, watercourses, or soakaways.

This stage provides assurance that the drainage system is safe, compliant, and fully operational.

Determining Drainage Capacity

The performance of a drainage system depends on:

Pipe Diameter: Larger pipes allow higher capacity but involve greater installation effort.

Gradient: Slopes that are too shallow may cause blockages, while excessively steep gradients may erode pipework.

Flow Rates: Calculations based on rainfall intensity, site occupancy, and peak demand.

By applying these factors accurately, systems are designed to handle both everyday use and extreme conditions.

Brownfield Site Considerations

On previously developed brownfield sites, it is often possible to reuse parts of the existing infrastructure, provided they meet current standards. Strategies may include:

Connecting to existing public sewers.

Relining or upgrading older pipework.

Utilising existing soakaways or discharge arrangements to watercourses.

This approach can reduce both costs and environmental impact, offering a practical and sustainable solution.

Expertise You Can Rely On

With extensive experience in flood risk management, below-ground drainage design, highways planning, foul sewage assessments, and geotechnical surveys, our team provides integrated solutions that support wider site infrastructure. By engaging with us at the earliest stage of development, you benefit from expert advice, efficient design, and systems that deliver best-value engineering.

Syntegra Group is committed to providing drainage facilities that are safe, reliable, and sustainable, ensuring your development runs smoothly from planning to completion.

The Importance of Getting Infrastructure Right

Well-designed drainage is not simply about compliance—it underpins the long-term success of a site. A properly engineered system ensures:

Smooth day-to-day operation.

Reduced risk of flooding or water damage.

Lower maintenance and repair costs.

Sustainable water management practices.

Working with a trusted partner like Syntegra Group ensures your development benefits from systems that balance compliance, cost efficiency, and environmental responsibility.

Get in Touch

Securing the right drainage solution is essential for the success of any project. Our team provides a full-service approach—from surveys and design through to installation, testing, and regulatory approval.

Contact Syntegra Group today to discuss your project and arrange an initial consultation. Early involvement helps ensure maximum compliance, reduced costs, and long-term sustainability.