Fats, oils and grease left over from the Christmas dinner should not be poured down the kitchen sink – amid fears they could cause flooding.

Severn Trent Water today warned householders to avoid tipping residue from turkeys down drains or risk major blockages. Figures reveal 20,000 blocked sewers were tackled in the region last year, with around 30-40 per cent of these blamed on build-up from fat and oil.

They say there is always a marked increase of blockages over the festive period. In a year, it costs Severn Trent £5-6 million a year to tackle.

Steve Dawes, sewerage manager for the water company, said today: “Many of our customers are aware of the danger that pouring fat, oils and grease down the sink will cause, but there is still a large proportion who are risking sewer flooding by discarding of fats in this manner.

“Fat, oil and grease in liquid form may not appear to be a problem but, as it cools, it congeals and hardens, settling on the walls of the cool sewer pipe.

“Over time this will build up, collecting other fat and debris, and will prevent the flow of waste water from passing through.

“With no way through the pipe, the waste water backs up in the sewer system.He added: “The only way to rid the sewers of these fat blockages is to use a high-pressure jet to loosen the fat and wash it away, or in serious incidents, heavy machinery is used to dig the fat out of the sewer. All of this work costs money, and could easily be avoided if people didn’t use their kitchen sink as an extension of the dustbin.”

In order to dispose of the liquids correctly, Severn Trent suggest they should be poured into an empty container and left to harden, and then be discarded in the kitchen bin, or wiped out of the roasting tray with paper and put in the bin.