Keeping Foul Sewers Foul: Why Construction Standards Matter

New developments continue to place growing demand on the public sewer network, making it essential that foul, surface and groundwater flows are managed correctly from the outset.

Why separation matters

One of the most important responsibilities for developers is ensuring that new sewers are designed and constructed in a way that prevents surface water and groundwater entering foul systems. Even small amounts of these flows can create significant downstream challenges, reducing capacity, increasing the risk of sewer flooding and placing added strain on pumping stations and wastewater treatment works.

Managing surface water

Modern standards require surface water to be managed independently wherever possible through appropriate disposal methods. Allowing rainfall to enter foul systems is no longer acceptable and directly undermines the resilience of the wider network. With increasingly unpredictable weather patterns, keeping rainwater at source remains one of the most effective ways to protect both new homeowners and existing communities. If developers encounter difficulties managing surface water during the construction phase (such as persistent runoff, temporary drainage constraints or challenging ground conditions) they should speak to us as early as possible. We can advise on suitable options to manage flows safely and compliantly.

Preventing groundwater ingress

Preventing groundwater ingress into newly constructed sewers is equally important. Infiltration often arises from poor jointing, incorrect bedding, deep trenching, damaged pipework or insufficient inspection before adoption. Once groundwater enters a foul sewer, flows can rise rapidly during wet weather, increasing energy use, operational emissions and the risk of hydraulic overloading. Ensuring high construction standards, correct materials and thorough quality checks is essential to safeguarding new assets before they become part of the public system.

The benefits and importance of high-quality construction

Good drainage design and robust construction practice support a smoother sewer adoption process, reduce the need for remedial work and help water companies maintain environmental and capacity compliance. Developers who prioritize these elements contribute to resilient communities, reliable infrastructure and long‑term environmental protection. By treating surface water separation, ingress prevention and early engagement as core elements of site planning, developments can connect into the wider network with confidence and play a positive role in managing growth sustainably.

Get in touch to discuss your site and how we can help you manage drainage effectively.

Tel: 0333 321 4952

Email: newdevelopmentsewerage@nwl.co.uk