Underground Drainage Pipes

An underground drainage pipe is a length of hollow tube, usually plastic and between 110mm and 160mm in diameter, designed to carry wastewater away from properties and to the nearest sewer network. They form part of extensive networks held together by underground drainage fittings. 

Plastic, particularly uPVC, is now widely used for underground plastic drainage pipes because it is lightweight, easy to handle, corrosion resistant and easy to cut and install. Other materials are also available that may be better suited to certain applications, including cast iron. See our guide to the different types of underground pipes for more information.

Plastic is the new industry standard thanks to a range of benefits it offers:

• Lightweight and easy to handle: Plastic is light, making it easy to transport, handle, cut and install.
• Cost-effective: Its lightness also makes plastic cost-effective to transport and it’s usually less expensive to produce too.
• Durable and corrosion resistant: Plastic is highly durable and resistant to corrosion, lasting as long as 50 years or more with proper installation.
• Eco-friendly: Their long lifespan and recyclability make plastic pipes an eco-friendly choice. 

The best underground drainage pipe will vary by application. Different situations and drainage needs call for different sized pipes. For example, 110mm drainage pipes and fittings are well suited to smaller domestic applications, whereas 160mm pipes are more appropriate for larger domestic and smaller commercial properties.

Underground pipes for drainage are used to move wastewater, rainwater and excess surface water safely away from buildings and external areas. They form part of a wider below-ground drainage network, helping manage foul and surface water separately, supporting soakaways or mains drainage connections and protecting buildings, landscaping and infrastructure from water-related issues.

Yes, our drainage pipes are compatible with a host of other drainage systems we supply. Because our underground drainage pipe range features several different sizes and is made from uPVC, the pipes can match different-sized openings, and can also be easily cut to accommodate precisely measured connections to drainage systems like inspection bases and risers, sewage treatment systems. You can also use our flexible, underground drainage adaptors to simply connect two different-sized drainage pipes together.

Our main drainage pipes for underground use are available in 110mm and 160mm diameters. The 110mm range is commonly used for smaller domestic and lighter-duty systems, while 160mm pipework is better suited to larger domestic, light commercial and higher-capacity drainage needs. 

The correct pipe size for your needs will always depend on factors such as expected flow rates, the overall size of the drainage system, any gradients and the total number of connections feeding into the run. Smaller systems commonly use 110mm pipework, while higher-capacity systems may require 160mm pipes instead. For a more detailed breakdown, see our underground pipe sizing guide.

Our underground plastic drainage pipes are available in both 3 m and 6 m lengths across the 110mm and160mm ranges, with plain-ended and single-socket options available in each size. We also stock 6 m half-perforated pipe in both diameters. Longer 6 m runs reduce the number of joints required, while 3 m lengths can be easier to handle where access is restricted.

Plain-ended drainage pipes maintain the same external diameter along their full length and require separate couplers to join different sections together. Socketed pipes feature an enlarged socket at one end, allowing the next pipe to connect directly. The best option for your needs will depend on the layout of your installation and the fittings required. 

Underground pipes are generally connected using push-fit sockets, couplers, bends, junctions and other adaptor types, depending on the layout and pipe types involved. Flexible adaptors can also be used where different pipe materials or diameters need to be joined. See our guide to connecting underground pipes for more detail.

The required depth for drainage pipes will vary based on type and local regulations. For example, sewer pipes will typically be placed deeper than domestic drainage. For domestic drainage, a depth of between 600mm and 900mm is common, to protect the pipes from freezing and shield them from surface disturbances such as traffic.  

Underground pipes should be laid at a suitable gradient so gravity can maintain effective flow, which also helps reduce the risk of blockages. Approved Document H provides minimum gradients based on factors including the type of drainage, pipe diameter and expected flow, with different requirements for foul and surface water systems. Always check the relevant guidance and project specification when determining the correct fall, and if you need further guidance, don't hesitate to contact the expert team here at Drainfast.

Every underground drainage pipe we sell carries a BSI Kitemark and adheres to the relevant industry standards, including being manufactured under BS EN ISO 9001:2015 and tested to the requirements of BS EN 13598-1:2010, BS EN 1401-1:2009 and BS EN 13476-2:2018. Along with the pipes we source from our manufacturing partners, our own Vision Drainage brand complies with the relevant industry standards.

All underground pipes we sell come with discounts on bulk orders, with up to 30% off when you spend over £3,000. You can also benefit from more discounts and benefits by signing up for a trade account with Drainfast.