Cameras are used to check if sewers are clear

The company said congealed chunks of fat were blocking up to 20% of drains and it was spending about �1m a year to clear out sewers.

Many water users contribute to the problem by not disposing of fat properly before washing dishes.

Some areas can take eight hours to clear using water pressure strong enough to cut pieces of timber in half.

John Perriam of South West Water said: "The fact is that blockages occur in large numbers, not just in our sewers, but also in private drains.

"It's very easy to forget what happens after you pull the plug in the sink."