The man in the street does not realise what lies beneath - that is, until it's causing a problem. Barry Bros. General Manager, David Maple, explains.

Drains, the forgotten assets of a council or sewer authority, form the underground backbone of an industrialised community. Barry Bros. has been cleaning drains for more than 40 years and has been instrumental in the evolution of drain cleaning practices.

Drains must be free running and big enough to support the flow involved if they are to perform effectively. However, community growth and the overtaxing of traditional construction materials and methods mean drainage capacity is often insufficient.

Older drains are usually made of terracotta with short lengths and many joins. Tree roots and obstacles often get caught, causing blockages and a build-up of material which can lead to flooding.

Drains close to the sea, particularly stormwater pipes, sometimes have minimal fall.This leads to clogging, through tidal movements, which reduces the drains' effectiveness, as sand becomes lodged in the pipe.

A core part of the Barry Bros. business is clearing blockages and removing material from drains with combination units - vehicles with a water pump and vacuum system.

The pump is connected via a 100 metre hose with a 25 centremetre diameter, onto a water-jetting nozzle which is propelled up the drain.

The water pushes the debris and material back to the manhole where it is sucked up with the vacuum hose connected to the combination unit. The material is then stored in the truck body for transport to the waste site.