Identifying the Lay of the Land with Drain Mapping

Drainage pipework illustration

When buying (or building) a new property, it’s not just what’s going on above ground that needs careful consideration; it’s also essential to be aware of the health and location of the drain network underneath the premises.

Being informed as to where drain pipes are situated will help to dictate any construction work that is planned to take place on the land, as well as avoid any unfortunate incidents of drilling down through a pipe accidentally. That’s where drain mapping comes in.

What is Drain Mapping?

Housing estate map

Drain mapping, or tracing, is a technique used to accurately detail the depth and location of all drains, sewers, gullies and manholes underneath a plot of land, while also demonstrating how they are connected together and indicating direction of water flow. This helps developers and property owners to gain an insight into potential issues with new and existing builds, in terms of plumbing, connections to public sewers, the chance of pollutants infiltrating and any other obvious deficiencies.

The process is necessary for new builds, but also when work is being carried out on older properties where changes and updates of drainage systems have not been added to existing maps.

The maps themselves are produced topographically, often with the use of tracing dyes fed down manholes – and occasionally using radio wave technology. Some drainage companies will provide DVD footage from CCTV drain surveys as part of the mapping service.  

Benefits of Drain Mapping

Millions of holes are dug into the road network here in the UK every year in order to locate, repair and install drains and sewers. This is invasive work and causes disruption for pedestrians, motorists and those living nearby. Drain mapping can help to reduce the number of unnecessary roadworks that cost billions in lost business and can potentially be detrimental to the surrounding environment.

It’s not just property owners that can benefit from a drain mapping survey, either. Construction firms looking to gain approved contractor status before carrying out work on a site are required to first produce a pre-qualification document, part of which must include a full and detailed drainage report.

Similarly, if a property owner suffers from drainage issues – whether a blockage or standing water that isn’t draining – having an updated map of pipe and sewer location will knock time and unnecessary work off for any drainage company called out to rectify the issue. The experts will be able to determine the site and nature of the problem far easier if they have a good understanding of waterflow and where systems are connected.


When it comes to determining the layout of the drains and sewers under your home, Express Drainage Surveys are the leading providers of drain locating and mapping in the South East.

Our expert team are available to chart the exact positioning of drainage systems, ideal for those considering purchasing a property or having work done on an existing one.