Squeamish readers may want to look away now – because the picture here shows just what happens to all the fat poured down sinks and drains in the Black Country.

The congealed fat clings to sewer walls and can build several feet thick unless it is regularly cleared by strong-stomached workers.

The grisly sight came to light when the Express & Star ventured into the sewers with Severn trent staff.

And, frankly, you wouldn’t believe what people put down their drains – a Ford Escort dashboard, a teddy bear and even a cow and a telegraph pole are among the bizarre items that have turned up. Then there are the dozens of road cones, knives and forks, £5 notes, false teeth and golf balls.

But one of the most disgusting and troublesome of items is the vast amount of congealed fat that gathers in the drains.

Andy Spedding, 52, from Aldersley, Wolverhampton, a senior technical operator with Severn Trent for 20 years, says the walls of underground pipes are cold, so as warm fat moves through the pipe it cools and settles on the walls.

“Even flushing hot water down with the fat will not stop this, as the surrounding ground keeps it cool,” he says.

“The fat will build up within the pipe over a period of weeks or months and eventually the pipe will become totally blocked.”

He added: “My own home filled up with sewage and it was due to nappies being flushed down the toilet by a neighbour.

“It used to be illegal to put anything other than natural waste into the system – people’s bills would come down if they stopped putting rubbish down the drains and toilet.

“Also, due to the increase in fast food outlets, the amount of grease and fat being poured into drains has increased rapidly.”

Phil Gelder who has worked for Severn Trent for 19 years and is sewerage asset manager at the Barnhurst site in Wolverhampton, said: “We find around 30 golf balls a week in the system and most of these will have dropped into the sewers off the streets.

“A lot of people think when something is flushed into the sewers it’s out of their hands. When there is a road accident involving a lorry carrying dangerous substances it all gets washed down the drains, and then we have to deal with it.”

Between 2005 and 2010 Severn Trent Water is investing around £850 million maintaining and improving river quality and more than £350 million improving sewers and dealing with sewer flooding.

It is also putting £400 million into maintaining water supplies and £150 million improving drinking water quality.

Phil says the sewerage system is a fairly simple idea that was brought to Wolverhampton in the 1860s.

“Water comes in from toilets, washing machines, drains, man holes and sinks and when it comes into the plant we have to filter out grit and stones that are larger than around 6mm,” he says. “The sewage flows into our six large tanks where it settles and the slurry falls to the bottom and the water and organic matter sits on the top.”

Microscopic bugs, called protozoers, live in the tanks and they eat the bacteria in the water. “It is an fascinating thing that still amazes me today,” says Phil.

“The bugs are a self-sustaining bio-mass that reduce the bacteria and leave the water clean.The water is filtered away into the river and the bugs stay in the system.”

The rainwater that has come in through the drains is siphoned off into Graisley Brook. “One of the most important things in the world is clean water and we are our own self-polluters, says Phil, “The sewers and drains are like your veins – if you look after them they will look after you.”