Thames Water is highlighting the challengess and costs of removing concrete dumped in its sewer network – the utility spends an estimated £1.6 million every year clearing hardened concrete from its sewer network.

Thames Water has over 60 concrete abstraction jobs running at any one time with big jobs taking thousands of engineer hours to remove.

Concrete is removed using ultra-high-pressure water jets to break it down at a pressure of 35,000 psi before it can be sucked out.

The water company says the problem is linked to building companies failing to dispose of waste correctly, from its pipes. Concrete can permanently damage the sewer network, disrupt services for customers and poses a significant environmental risk.

Thames Water is seeing repeated incidents where building firms are disposing of commercial construction waste directly into the sewer network. Over the past 12 months, engineers have spent thousands of hours removing solidified concrete from pipes across London and the Thames Valley region. The process requires specialist high-power water jets to break down the concrete into small pieces so it can be safely extracted without damaging the pipes. The pressure is equivalent to placing the weight of a large SUV onto an area the size of a thumbnail.

Concrete build-ups in pipes are identified using ultra-sensitive sewer sensors, which alert engineers to obstructions in the network or are detected when blockages lead to sewer flooding. If left untreated concrete down the sewer network restricts wastewater flow that can then cause wastewater to back up on to streets, homes, schools and businesses. It can also cause significant damage to the pipework, with repairs costing millions.

Tim Davies, Head of Waste for North London, said:

“We are urging construction companies to be more vigilant in their disposal of concrete, to prevent damage to our sewer network, as it takes valuable time and resource away from essential infrastructure upgrades. The concrete removal process can be extremely complex. In many cases, we use high-pressure cutting units to break down concrete within the sewer before it can be safely removed. This work requires significant investment with expensive equipment, a large team of skilled engineers, and a considerable amount of time to complete.

“Our teams are working closely with construction companies across our communities to raise awareness of the serious damage and disruption caused by improper disposal. My message to businesses and contractors is simple: please ensure concrete is disposed of correctly. Preventing this issue in the first place is far more effective than dealing with the consequences later."

Discharging concrete into the sewer network is illegal and can result in enforcement action, with companies liable for the cost of repairs and potential prosecution. Thames Water’s network protection teams investigate incidents and trace concrete back to construction companies who are then asked to contribute to the cost.