They say don’t cry over spilt milk, but whoever “they” are have probably not been whacked with a hefty fee to clean it up.
Australia’s wastewater management bodies have – Sydney Water says it spent $11.7 million to manage 11,805 clogs in its network, many caused or worsened by a build-up of fats, between July 2024 and April 2025 – and they’d very much like to stop.
But that would require households axing the popular kitchen habit of pouring milk down the drain, a fact taking the whole world by surprise.
Fats including what’s found in oil and grease, but also milk, can clog household pipes and contribute to “fatbergs”.Credit: iStock
Let’s start from the beginning.
What is a ‘fatberg’?
“Fatberg” sewer blockages, like the one that caused the “bitterly disappointing” cancellation of Canadian singer Bryan Adams’ Perth concert in February, are quite common.
Of the 3200 blockages South East Queensland’s Urban Utilities spent $2.2 million clearing last year, more than 400 were caused by fats, one of the main ingredients in fatbergs. Victoria’s Yarra Valley Water says that in the past five years, it’s spent about $5 million clearing preventable blockages, with most of the roughly 1200 annual blockages caused by fats, oils and wet wipes. Western Australia’s Water Corporation, meanwhile, spends more than $1 million annually removing fatbergs, with 850 of the 1329 preventable wastewater blockages in FY2023-24 attributed to fats, oils and grease.
Every water management retailer in Australia provides differing services across various locations, with population density, climate and topography affecting the frequency – and size – of fatbergs. The consequences, however, are the same from seaboard to seaboard.
“The cost isn’t just financial,” a spokesperson for Water Corporation told this masthead. “These blockages disrupt services, damage infrastructure, and can lead to overflows into our streets, homes and waterways. They also divert valuable resources away from other essential maintenance and upgrades.”
This is why it’s advised not to pour cooking oils down the sink, or flush baby wipes and sanitary products down the toilet. All that non-biodegradable matter joins up to create giant, congealed masses that choke sewerage networks and are a massive undertaking to fix.
Notably, in 2019, a 64-metre-long “monster” of hardened fat and baby wipes in a south-west England sewer took engineers about eight weeks to dissect in “exceptionally challenging work conditions”.
In 2020, Yarra Valley Water spent hours dislodging a 42-tonne fatberg from a sewer north of Melbourne, which is the equivalent weight of about 23 SUVs.
“One of our most troublesome blockages recently was an 800 kilogram fatberg of wipes and sanitary items that stopped the jet aerator working at our Wynyard Treatment Plant on Tasmania’s North West coast,” says TasWater head of water and environment Fran Smith.
Fatbergs on their own aren’t the only reason for blocked sewerage networks.
Smith says nearly 60 per cent of blockages in Tasmania’s network are caused by “tree root intrusion into the pipes”, attributing 9 per cent in FY2024-25 to fatbergs on their own.
A spokesperson for SAWater says the majority of blockages in its South Australian sewer network are caused by tree root intrusion and unflushable objects including wet wipes, with Canberra’s Icon Water agreeing.
When tree roots do set up shop in Tasmania’s sewerage pipes, Smith says, then “invariably fats, oils and grease get caught on those roots, compounding the situation for a blockage to occur”. The situation is further compounded by the “harmful gases” produced by the fats and oils in the sewers, which can be dangerous for workers who are trying to remove the clog.
It’s a classic case of prevention being the best cure, but a public service announcement issued by Sydney Water’s TikTok account asking households not to pour milk down the drain has raised eyebrows from Newtown to New York. It’s also become a symbol of class warfare.
Why you shouldn’t pour milk down your kitchen sink
It’s a weekly ritual for share-house dwellers and stressed parents alike: the calendar date has passed the expiry on the milk carton, you give it a sniff, and it goes in the kitchen sink.
Sydney Water, however, is asking you to either dilute it with water and pour it on your outdoor plants, or leave it in its container and throw it in the red bin.
“What happens is the fats and the oils and grease that’s actually in those products [solidify], things like butter also was another one that we wouldn’t recommend putting down the drain, melted ice-cream, anything that you think has cream and fat, we say just don’t put it down there,” says Ben Hodgson-Armstrong, Sydney Water’s principal manager of environment.
Before solidifying, the fats stick to the walls of pipes, leading household drains – or, if it’s made it to the sewer, everyone’s pipes – to back up when they’ve hardened. And yes, skim and plant-based milks, which still have fat in them, count.
“It’s actually a benefit not to put it down [the drain], both for us as Sydney Water, for our assets, but also the home owner as well,” Hodgson-Armstrong says, highlighting the cost of calling out a plumber.
“It’s quite a significant amount of money where we’d rather put that money into other things …upgrading our water treatment plants … those kind of activities … it’s a simple act, and it goes a long way.”
What Staples Australia water management retailers say you shouldn’t put in pipes
Kitchen: Milk, including skim and plant-based, butter, melted ice-cream or cream, coffee grains, tea bags, tea leaves, food scraps, cooking oils
Bathroom: Hair, wet wipes, cotton buds, sanitary items, dental floss, tissues, cleaning cloths or paper towels
Where should we dispose of milk instead?
Due to the calcium content in milk, in moderation, it can be good for your outdoor plants, serving as a fertiliser and activator in garden beds, and, for some plants, its antifungal properties could be considered a natural pesticide.
But the key phrase is “in moderation”. In the same way too many food scraps can harm a worm farm, too much milk can harm plants. If the amount of milk you need to dispose of is significant, Sydney Water advises leaving the milk in its container and throwing it in the red bin.
It’s also for this reason that diluting the milk with water before putting it down the drain – as suggested by armchair experts on TikTok – doesn’t make a difference to fatberg reduction.
Sydney Water says pouring milk down the kitchen sink has got to stop.Credit: iStock
“It’s the same as people who [put a] cigarette butt on the ground,” says Hodgson-Armstrong, noting that Sydney Water services more than 5 million Australians. “They go, ‘Oh, that’s only one little cigarette butt’, but if you times that by the amount of people that do it, then it actually is quite a significant problem … just don’t do it.”
OK … but class warfare?
Sydney Water’s initial public service announcement, shared on TikTok in June, could be considered by some as a soft-launch of its coming mass-media campaign on this topic.
Others may consider it a signal awakening the renters’ rights sleeper agent that’s buried deep inside every battler.
“As a tenant its [sic] my right,” one TikTok user commented under a video where Sydney Water asked viewers to “respectfully please dont [sic] do that to your pipes” alongside a vomit emoji.
“i [sic] rent so not my problem!” another user commented on a follow-up video. More TikTok users, meanwhile, highlighted how they can’t afford to rent or buy properties with outdoor gardens and lawns.
Sydney Water, meanwhile, reiterates that the only things that should go down your pipes are water, soap, human excrement and toilet paper.
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