NI Water is urging customers to dispose correctly of fat, oil and grease left over from Easter dinners.
Each year, many people still tip fat, oil and grease down the sink, with disastrous effects on our drains.
NI Water said fat, oil and grease solidify as they cool and create blockages in the sewerage system, which often results in flooding. Last year NI Water dealt with 24,000 sewer blockages, nearly 30% of them caused by fats, oils and greases.
Nearly £1.7m was spent clearing drains and cleaning up.
Des Nevin, NI Water's head of networks sewerage, said: "Easter is a popular time for friends and families to get together, often to enjoy a roast dinner. While the meal may be planned with meticulous detail, little attention is paid to what we put down the sink.
"Fat, oil and grease in its liquid form may not look harmful, but once in the drains, it is.
"Even when hot water or soap is poured down the sink, the fat, oil and grease will still harden.
"Detergents and bleach may also appear to work, but this is only temporary.
"Each year we spend valuable resources fixing avoidable problems.
"When a drain becomes blocked and overflows, the consequences can be devastating.
"We can all play a part in maintaining the sewerage infrastructure from restaurants, pubs and hotels right through to home owners and industrial outlets."
One way to dispose of fat, oil and grease is to let it cool and solidify, and then scrape it into the rubbish bin, or it can be poured into a suitable container and taken to a council recycling centre. Plates, pots, trays and utensils should be scraped and dry-wiped before washing.