Those 'flushable' wipes sure are a gross problem. Combined with nappies (diapers), condoms, tampons and congealed fat, they can stick together to form a gargantuan 'fatberg', like the one currently clogging up a section of London's sewers.

At 130 tonnes (143.3 tons) and covering 250 metres (820 feet), it's the biggest ever unearthed in Britain.

That's as heavy as at least 20 African elephants, and as long as 2.5 football fields.

It was discovered earlier this month during a routine sewer inspection, and now workers are spending seven days a week trying to break it up so that it doesn't flood the streets of Whitechapel in East London with sewerage.

"This fatberg is up there with the biggest we've ever seen. It's a total monster and taking a lot of manpower and machinery to remove as it's set hard," said Matt Rimmer of Thames Water.

"It's basically like trying to break up concrete. It's frustrating as these situations are totally avoidable and caused by fat, oil and grease being washed down sinks and wipes flushed down the loo [toilet]."

These fatbergs have been a recurring problem with the rise in popularity of self-described 'flushable' wipes, which don't disintegrate in water and are therefore not actually flushable.

In 2013, a "bus-sized" London fatberg broke the world record for biggest ever, only to have the title stolen in 2014 by a London fatberg the size of a commercial plane.

Fatbergs have also been retrieved from sewers in Belfast, Ireland, Victoria, Australia, and Cardiff in the UK.

The eight workers are equipped with protective suits, high-powered jet hoses and shovels to break up the fatberg, which is expected to take around three weeks. They are removing 20 to 30 tonnes per day.

CCTV images show the sewer pipes completely blocked by the mass. Thames Water said it costs £1 million (US$1.33 million) per month to keep the sewers clear of these blockages, which accumulate quickly.

There is actually a use for the things, as disgusting as they are. Since 2015, Thames Water has been supplying low-carbon energy company 2OC with fats and oils retrieved from London's sewers.

These are burned in special generators that produce 130 gigawatt hours of electricity per year, enough to power 40,000 average-sized homes.

Although they'd still prefer people didn't send the stuff down into the sewers to start with.

"When it comes to preventing fatbergs, everyone has a role to play," Rimmer said.

"Yes a lot of the fat comes from food outlets but the wipes and sanitary items are far more likely to be from domestic properties. The sewers are not an abyss for household rubbish."