What is Drain Mapping, and Why is It Essential?

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What is Drainage?

The drainage system of any property comprises two parts: Foul drainage and surface water drainage. These two systems must be kept separate and ensure that they do not compromise each other. The foul drainage system carries the waste/used water from washing machines, dishwashers, bidets, showers, sinks, and toilets to the drain. The pipework and accessories above the ground are called sanitary pipework, while the underground network is known as foul sewers or foul drains.

Surface water drainage drains water from rain, ice, and melted snow from hard surfaces. Rainwater pipes and gutters above the ground are called roof drainage, while the underground system is known as surface water sewers or surface water drains.

Why is Underground Drainage Important?

When installing your drainage system, as in the case of a new building, you will have to consider the location and depth of the underground sewer or drain to which you will be connecting your drainage system.

If your property is to be constructed near or over a public sewer, you must execute an agreement with the sewerage undertaker. Therefore, you must consult your construction company before the civil works begin. Construction over a sewer or drain can damage them, causing them to get blocked or leak and leading to environmental damage, health problems, and foul odour. It will also complicate your construction project because you must repair faulty drains and remove blockages.

What is Drain Mapping?

Drain mapping is often called ‘asset mapping’ and involves the creation of a precise map of the underground drainage system of any property. It aims to accurately plot the locations of manholes, gullies, and pipes in a drainage system. GPS technology has made this job considerably easy and precise. Apart from mapping the locations of these utilities, it can identify the direction flow of piping, their sizes and depth levels, and which pipes carry foul water drains. Special software is used for carrying out this task along-with GPRS systems such as OSGM15.

Why is It Essential?

New Builds

Drain mapping is usually carried out before starting a construction project. It helps identify the scope and layout of the existing system underneath the construction area to avoid any damage to the drainage system. Once this information has been retreived, engineers and drainage experts can make better decisions. They can identify if the systems need to be upgraded or modified. They can also determine the best way to connect the new property to the main drainage system. The utility of drain mapping can be found in numerous industries. You will find construction companies, local councils, highway authorities, architects, and surveyors requesting a drain mapping service.

Carrying Out Other Construction Work

Other civil works, such as carrying out a house extension and building a driveway or patio, can also affect underground drainage systems. Patios and driveways need to have a slope so that water from rains or other sources flows towards the drainage utility. It also has to ensure that the ground is permeable so water can seep through it easily. These activities can reduce flooding risk and protect your patios and driveways. Surface water from these hard surfaces should not be allowed to drain onto main roads or highways, as it could prove dangerous and deteriorate these structures over time. When planning a house extension, care should be taken that it is not built on existing drainage/sewerage systems. If this is not done at an earlier stage and it is found that your construction work is damaging the underground drainage system, you may have to stop your work which will be a loss of money and time for you. Drain mapping services can help identify if there is any drainage system beneath the area before you begin any construction work.

Purchasing or Selling a Property

It also plays a significant role in influencing the purchase decision of a property as it can identify any serious problems in the drainage system. Some damages to drain systems can be highly expensive to replace or repair. Drain surveys may be enough for someone to decide whether he wants to buy a home, but drain mapping can be highly useful for a detailed picture. You will come across building surveyors who recommend drain mapping before you buy a property. If you are a seller and want your property to fetch the ideal price, availing of drain mapping services can help you identify any problems before advertising. That way, you can resolve serious issues and get the right price for your property.

Repair and Maintenance

Drain mapping can also help identify severe blockages, leaks, and any other problem with the drainage system. This makes repair and replacement work much easier. Plumbers and drainage experts can save considerable time with drain mapping. It can also predict future problems and repair them in time to protect them from more damage and, therefore, higher repair cost.

Flood Risk Management

Drain mapping can also be helpful in flood risk management as well as the prevention of pollution. Gaining a precise understanding of the underground drainage system can help experts in contingency planning in case of emergencies such as fire accidents, chemical spillages, and floods.


Drain mapping can be used for site compliance. Several commercial and public sites are required to comply with environmental and building regulations. Businesses can avail of these services periodically to identify any shortcomings and carry out remedial work in time to comply with these regulations

Water Flow Tracing

The simplest method of understanding the water flow is to check it at several stages throughout the route from entry to exit. This can be done by allowing the water to pour or run through the drain and inspecting the flow direction. This can be checked by opening a nearby manhole cover and seeing if the water is running through it. Another method is to flush a tissue paper in your toilet, lift the nearby manhole cover and follow where the tissue paper goes.

Water Test

Water tests allow experts to check whether elements such as waste or sewage are present in the water or if the water is clear. This can help you identify the water flow and make it easier for you to access the entire network.

Dye Tracing

Similar to the water flow tracing method, dye tracing uses colour dyes for tracing water. The dyes are usually poured into the sink, toilet, and even directly into the drains. Specially designed dyes are used, usually available in the form of tablets, which are eco-friendly and do not damage the installation. They also do not leave stains on toilets, sinks, or drains.

CCTV Surveys

CCTV drain surveys are the most comprehensive and advanced drain mapping method. The layouts and the locations of a drainage network can be easily identified using this method which involves lowering special CCTV cameras into the drainage system. The camera is then moved around the system, and video is recorded, which can help experts in countless ways. No excavation or digging is required as the cameras can reach all nooks and crannies.

Sonar Drain Tracing

Sonar drain tracing uses sound propagation to identify the location of pipes and other drainage installations under the ground. An active sonar system has a sound transmitter and a receiver. It creates pulses which are called ping. These pings detect echoes that can measure the distance between the sound source and the object. The electrical pulses can help identify specific features of the drainage network, which can further diagnose problems and issues.

Our Recommendation

Drain mapping is an essential service which should be availed when necessary, as we have mentioned above. Hire an experienced company which uses CCTV surveys to carry out drain mapping. This method is quicker, more affordable, and more precise. Whenever you carry out major construction work, make sure that your contractors are completely aware of the underground drainage system in that area to avoid legal troubles and save yourself from incurring losses. Remember, drainage and sewerage systems protect your property from several problems, including flooding, health issues, and infrastructure deterioration. Ignoring these systems to save any cost may make you lose more than what you were trying to save.

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