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Drainage & Plumbing

Lanes sends in a pig to root out blockage in school gas main


Lanes for Drains engineers in Derby have used poly-pigs to root out a blocked gas main that builders feared could delay the completion of a new school.

They were not the porky kind of pigs that go oink oink, but the plastic ones, because a poly-pig is a device that is used to clean out pipes.

A construction company called Lanes for Drains Derby depot on Riverside Park, East Service Road, Raynesway, after it discovered a new gas main, laid to serve the school they were building, had become blocked.

Chris Norbury, East Midlands Area Development Manager for Lanes for Drains, the UK’s largest independent drainage specialist, explained: “The pipe had been laid but not capped.

“When it rained, silt and debris was washed into the pipes and caused a blockage. Because the pipe was undulating up and down, within the ground, it wasn’t possible to use a jet vac to clean it out, so we turned to older technology, poly-pigging, to get the job done.”

Lanes Derby has a highly sophisticated jet vac tanker. Engineers guide the tanker’s high pressure hose into the pipe, which is then powered along the drain line using a powerful jet of water, forcing debris out of the pipe, either forwards or backwards, depending on what type of jetting head is attached to the hose. The jet vac can also be used to suck debris from a pipe.

However, the technique used for this cleaning job involved inserting a poly-pig, a cylinder made of flexible plastic or foam that is often shaped like a bullet, into the pipe, and forcing it along the run with compressed air.
The poly-pig is highly effective at clearing blockages and pushing material out of a pipe – and, because it is flexible, it can get round kinks and curves in pipes that jet vac hoses cannot.

Chris Norbury said: “Pipeline pigging, as it is called, is a very useful technique. In this case, 180 metres of pipe were pigged. Because the diameter of the gas main ranged from 180mm to 50mm, several different sizes of poly-pig were used.

“We were able to clear the blockage and the contractors could test the boiler in the new school. To their relief, it fired up first time, so the poly-pigs had done their job very well.

“It meant that the planned completion time for the project, linked to the need to open the building at the start of a school term, was not affected.”

So, next time your drain is blocked, a Lanes engineer might arrive with a pig under his arm – and that is not a porky!