The number of blocked sewers in the London area is expected to rise by 15% over the Christmas period because of cooking fat being poured down sinks.
Liquid fat poured down sinks quickly solidifies and blocks drains
Thames Water is urging customers to let fat from the Christmas roast cool and solidify, before putting it in the bin.
This year, the company cleared more than 70,000 blocked sewers, of which more than 60% were caused from fat, oil and grease poured down drains.
The blockages led to the flooding of some 2,000 homes and 5,000 gardens.
Fat and grease quickly cools and hardens in sewers.
When it mixes with other household times such as nappies and wet wipes, it can lead to blockages in the sewer pipes.
Thames Water advice
Pour cooking fat into old container or wrap it up once it has cooled
Make bird feed by mixing fat with high nutritional content - such as beef or lamb fat - with seeds, dried fruit and food scraps
Use turkey fat for gravy or goose fat for roast potatoes
Phil Aldous, from Thames Water, said: "Sewer flooding is a particularly upsetting experience for customers.
"We can all help to avoid it by letting fat cool and scraping it out with a spoon into a box or bag, or wrapping up the solid fat and disposing of it in the bin."
He added: "It's not just out sewers which have problems, but customers' pipes which link their property with the public sewers. They are most at risk as they are narrower and block more easily."