Underground Drainage

When it comes to managing foul and surface water safely and efficiently, underground drainage is essential. At Pipestock, we supply the complete range of Polypipe PVCu Underground Drainage systems – trusted across the UK for their strength, reliability, and ease of installation. Whether you’re working on a domestic extension, a new-build development, or a commercial project, our PVCu solutions provide everything you need to build a fully compliant and long-lasting system.

PVCu (unplasticised polyvinyl chloride) has become the material of choice for below-ground drainage in the UK. Here’s why:

• Durability – resistant to corrosion, chemicals, and soil conditions.

• Lightweight handling – much easier to transport and install compared to traditional clay or cast iron.

• Ease of installation – innovative seal and snap-cap push-fit system allows quick assembly without specialist tools.

• Comprehensive approvals – Polypipe’s PVCu range is fully certified:

  • BS EN 1401-1 – for plastic piping systems in non-pressure underground drainage and sewerage.

  • BS EN 13476 – structured-wall piping systems.

  • BS 4660:2000 – specification for underground drainage and sewerage systems.

  • Kitemark Licences – KM 59284 and KM 06383 ensure independent quality assurance.

• UK Manufactured – made to the highest standards, with reliable availability.

The result is a system you can trust, backed by decades of Polypipe expertise.

Underground drainage is designed to move both foul water (from toilets, sinks, and appliances) and surface water (from rainfall and paved areas) away from buildings. The system works on gravity:

• Pipes are laid to a gradual fall.

• Wastewater flows through to inspection chambers, gullies, or soakaways.

• The network ultimately discharges into the public sewer or a private treatment system.

A well-planned and properly installed system ensures smooth flow, prevents blockages, and protects properties from flooding or water damage.

Choosing the correct pipe size is crucial. Polypipe PVCu underground drainage is available in 82mm, 110mm, and 160mm diameters, each suited to different applications:

• 82mm (3”) – typically used for smaller connections such as rainwater downpipes or limited surface water drainage.

• 110mm (4”) – the most common size in domestic systems, used for foul water runs from toilets, bathrooms, and kitchens, as well as surface water from driveways and patios.

• 160mm (6”) – a larger capacity option, often used in commercial systems, housing developments, or where multiple properties connect into one run.

Most domestic projects use 110mm pipe, while 160mm is reserved for higher flow rates. 82mm is usually for rainwater downpipe connections.

• Gardens and non-trafficked areas – typically 600mm minimum cover.

• Driveways or trafficked areas – 750mm or more to withstand load.

• Always check local building regulations for site-specific requirements.

Yes. Polypipe offers bends at 15°, 30°, 45°, and 87.5°.

• Use gentler bends where possible to aid flow.

• Inspection chambers or rodding points should be placed at changes of direction for maintenance access.

• Chamfer the pipe ends.

• Apply silicone-based lubricant.

• Push into the socket until it clicks with the seal and snap-cap system.

• Adaptors are available to connect PVCu to clay, cast iron, or other pipe materials.

• Excavate the trench to the correct depth: usually 600mm in gardens and 750mm in driveways.

• Lay a granular bedding (around 100mm of pea shingle or similar).

• Cut and chamfer the pipe ends, apply lubricant, and push-fit into sockets.

• Maintain a steady gradient (1:40 for foul water, 1:100 for surface water).

• Include access points at junctions and bends for future maintenance.

• Backfill carefully with selected material, testing the system before final reinstatement.

• Check site plans and inspection chambers.

• Use electronic pipe tracing equipment for buried systems.

• Drainage surveys may be needed on older or unrecorded systems.

• Minor cracks/damage: cut out the affected section and replace with new pipe and double-socket couplers.

• Severe issues: excavation and full replacement may be required. Always ensure repairs maintain the fall and integrity of the system.

• Materials: PVCu pipes and fittings are cost-effective.

• Labour & excavation: typically the largest part of the expense.

• Project size: simple domestic systems may cost a few hundred pounds, whereas larger developments can run into thousands.

The Polypipe PVCu range provides a full suite of drainage components:

• Pipes – plain-ended and socketed, perforated or solid wall.

• Fittings – bends, junctions, reducers, couplers.

• Bottle Gullies – collect debris and prevent smells.

• Channels – surface water drainage solutions.

• Access Points & Chambers – for inspection, rodding, and maintenance.

• Tools & Accessories – lubricants, cutters, and solvent cement.

Each component is designed to work seamlessly together, ensuring compliance and long-term performance.

• Quick push-fit assembly with innovative seals.

• Lightweight and easy to handle on site.

• Strong, impact-resistant PVCu for long service life.

• Compatible with clay, cast iron, and other legacy materials via adaptors.

• Full range of sizes and fittings for a complete system solution.

With its UK manufacture, Kitemark approvals, and complete product range, Polypipe’s PVCu underground drainage system is one of the most reliable choices available. Whether you need 82mm, 110mm, or 160mm pipework, plus all the fittings, gullies, and chambers to complete your project, Pipestock has you covered. Backed by technical expertise, compliance with British Standards, and years of proven performance, this system gives you confidence that your underground drainage is built to last.