HUGE lumps of congealed fat are putting the pipes of Oxford’s sewer network at risk of collapse, it has been warned.

Thames Water yesterday said it was launching its “biggest push yet” to tackle the problem of the so-called fatbergs, which are costing millions of pounds to remove.

The blockages are formed when cooking fat is poured down sinks and mixes with items such as wet wipes, sanitary towels and cotton buds flushed down toilets, before hardening in the pipes.

Fatbergs vary in size and one of the biggest recently discovered was in London and weighed 15 tonnes.

And more are being discovered in Oxford every week by the firm’s engineers as they carry out an unprecedented review of the city’s sewer system.

Thames Water fatberg expert Craig Rance said: “Sewers aren’t magic portals, it all has to go somewhere.

“Pouring leftover cooking fat and oil down the sink blocks pipes, it’s as simple as that.

“When we’re out cleaning the sewers or repairing the damage caused by these fatbergs we often have to use noisy tankers and close roads so it impacts on everyone.

“The traffic chaos caused by this work is completely avoidable, but if homes and businesses in Oxford continue creating these blockages nothing will change.”

Mr Rance revealed that the company spent £25,000 alone last year clearing the fatberg that formed under Park End Street, causing the sewer to collapse.

The work brought traffic in Frideswide Square to a standstill.

Mr Rance added: “It really is a massive and very expensive problem.”

And the problem could pose a threat to the wider sewer network if homeowners and businesses do not change their habits, it was claimed last night.

Thames Water spokeswoman Becky Trotman said clearing the fatbergs requires high-powered jets, which could damage the lining of sewers and increase the risk of collapses.

Ms Trotman added: “We are now launching our biggest push yet to tackle this, because it has got to the stage now where it is a massive problem.”

As it carries out its review of Oxford’s sewer network – launched jointly with Oxford City Council last October – Thames Water said it was discovering several blockages in the main “trunk sewers”, which connect the city centre to the sewage treatment works near the Kassam Stadium.

Engineers have been dealing with the fat build-ups as they go, but a fresh drive to raise awareness has now been launched.

Thames Water said yesterday it had written to 200 businesses in Oxford and the company is also going door-to-door to speak to customers and identify problems.

In particular it is focusing on businesses handling food, with the aim to reduce the amount of cooking oil and fat finding its way into the sewers.

Ms Trotman said clearing work so far had been focused on pipes under Christ Church Meadow and the university playing fields area that connect to the Littlemore pumping station.

Oxford Mail:

  • Grotty problem: A build-up of solidified fat, known as a fatberg, between Christ Church and Littlemore 

She added: “We have been pro-actively surveying and have cleared a lot of fat out of the pipes since we started this work.

“But we look after 43,500 miles of sewer pipes and can’t monitor them all the time, so fat can quickly build up.”

The worst affected areas in Oxford include Frideswide Square, Botley Road and Cowley Road, where sewers converge.

Through its review of the sewers, Thames Water has also decided to bring in a specialist team from London to “clean and optimise the performance” of the pumping station at Littlemore, which sends about 90 per cent of sewage in the city to a treatment plant.

The progress on the sewerage review – now about half-way through – was welcomed by Oxford City Council. Flood scrutiny committee chairman Roy Darke said: “Where Thames Water has been finding problems it has been dealing with them and we now think there have been improvements and fewer problems.

“That does not mean there will not be a need for major fixes to infrastructure, but when the study is finalised they will produce a strategy next year.”