Flushing cooking oil from the Christmas turkey might just cause a festive monster fatberg in the sewers under the streets, Thames Water is warning.

%image(14922699, type="article-full", alt="Is this a fatberg monster beneath your home? Picture: Thames Water")

Millions of households admit they flush oil down the sink and sanitary products down the loo, believing that it’s no longer their problem once it’s past the U-bend and out of sight, the company’s research has found.

Nearly 7,000 fatbergs lurked in the sewers across east London in just 12 months, from Aldgate right out to the M25.

Prime culprit was the Whitechapel fatberg as long as two football pitches and weighing 130 tonnes, the same as 11 London double-decker buses, discovered last year.

“We have to fight the fatbergs,” Thames Water’s Henry Badman urged.

%image(14922700, type="article-full", alt="Piece of East London's social history... Katie Balcombe looks at remnant of Whitechapel fatberg at Museum of London. Picture: David Parry/PA")

“It may seem easier to pour cooking oil into the sink or flush wet wipes down the loo—but this can lead to blockages which have a devastating impact on the environment.”

It costs £18 million every year clearing blockages in London, nine-out-of-10 of them fatbergs caused by wet wipes, nappies and sanitary products mixing with cooking oils. The lumps harden to enormous size, often completely blocking the Victorian sewage network that wasn’t designed to cope with today’s ‘throw away’ society.

A Thames Water survey found four-out-of-10 households admit pulling the toilet chain on sanitaries “for convenience” rather than put it them in the bin. There is confusion over packaging that says ‘flushable’, especially wet wipes.

London had 41,000 fatberg blockages in the 12 months to April alone.

%image(14922701, type="article-full", alt="Christmas Fatberg: "So this is east London... but do they know I'm coming?" Artwork: Nathan Wright")

But the East End wasn’t as bad compared to the leafy suburbs, with Tower Hamlets having just 378 blockages, the sixth lowest across London, and neighbouring Hackney 526.

The further out you get, the more fatbergs blockages. Both Newham and Barking & Dagenham clocked up almost 2,000 fatbergs each, though nowhere near as big as the Whitechapel monster. Redbridge had more than 2,000 while Havering recorded 2,331.

Some parts of London have had a much harder time. Worst of all was Hounslow with almost 2,500.

The reason some areas get off lightly is ironically a lack of separate drainage, Thames Water explains. Outer suburbs have separate drainage from the sewage. So foul sewage is more prone to blockage from wetwipes and toilet waste.

%image(14922702, type="article-full", alt="Artist impression of sewer fatberg under the streets. Picture: Thames Water")

Rainwater in older districts like the East End, however, goes straight into the sewers which actually helps dilute blockages.

Yet that didn’t explain the monster of all time, the Whitechapel fatberg in 2017, part of it now on public show at the Museum of London, which took three weeks to shift.