As South Australian families prepare festive feasts and children unwrap new toys, households are being urged to keep cooking fats and oils well away from sinks and toilets to avoid smelly and disruptive sewer blockages.

SA Water’s Healthy Sewers campaign reminds residents that simple actions in the kitchen and bathroom can prevent major problems in pipes on their property and in the street.

This Christmas, excess cooking fats and oils should be left to cool before being scraped into the bin, food scraps caught with a sink strainer, and toilets kept for the four Ps only – pee, poo, (toilet) paper and products with proof of flushability.

SA Water’s Senior Manager of Infrastructure, Planning and Strategy Dr Daniel Hoefel said across the state, there have been 5,167 sewer main blockages so far in 2025, with 1,146 incidents – or 22 per cent per cent - linked to avoidable build-ups of cooking fats, grease, wet wipes and other foreign objects, including small toys flushed during holiday excitement.

“Non-flushable items entering the wastewater network this year contributed to 624 blockage incidents – or 10 per cent of the annual total – which is a decrease from last year with 749 blockages, or 15 per cent of the 2024 total (4,331 blockages),” Daniel said.

“This year’s total sewer blockages sets a record for SA Water, up from 4,331 last year. Tree root intrusions were the most common cause, contributing to 3,342 incidents or about 65 per cent of blockages. That is an increase from last year’s total number of blockages caused by tree roots (2,442 incidents).

“These blockages can force raw sewage back into homes or into the environment, creating serious health and hygiene risks, along with inconvenience and mess.

“At the Bolivar Wastewater Treatment Plant, our crews remove about 120 tonnes of wet wipes, congealed fats and other debris each month.

“While this represents the end of the sewer network, the fact huge amounts of these items that can cause blockages are still present in the system means there is a higher – but avoidable – risk of blockages closer to homes and Christmas lunches.

“Once these materials merge in the sewer network, they form dense, greasy masses that resemble foul-smelling grey-brown lumps – also known as fatbergs.

“Slimy on the outside and solid in the middle, fatbergs trap anything passing through the pipes and emit strong sour odours as they obstruct wastewater flow.

“Although screening equipment removes these materials before treatment, the waste must still be sent to landfill, which is a reminder that what goes down the drain has lasting consequences beyond the kitchen or bathroom.

“By keeping festive cooking fats, food scraps and toys out of the sewer, South Australians can help protect their homes, the environment and the state’s essential infrastructure throughout the busy Christmas period.”

In addition to sewer blockages, SA Water has seen a recent rise in odour complaints caused by dry gully traps, which are common features of residential plumbing.

Gully traps are external drains designed to prevent sewer odours escaping by maintaining a water seal. However, many are installed under outdoor taps and in newer homes may not be regularly flushed with water.
“Dry and hot weather can cause gully traps to dry out which then allows odours to escape,” Daniel said.

“We’re encouraging residents to regularly check their outdoor gully traps and top them up with water if they appear dry.

“While we have received customer complaints of this kind in previous years, it’s only became a noticeable trend in recent months, particularly in new development areas in Adelaide’s north.”

Sixty-five odour complaints were linked to dried gully traps in the past 12 months, compared to 50 in the previous year.