The seemingly harmless beverage causing massive damage when poured down the sink

When milk has gone past its used-by-date, many of us simply pour the remaining amount down the kitchen sink drain and think nothing of it.

While many of us know oil can't go down the drain, milk is a surprising one with 72 per cent of Sydney locals thinking it was OK to dispose of that way, according to Sydney water research.

But milk is just one of a number of items that can cause massive problems for waterways, the sewerage system and the pipes in our homes.

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Milk and other items incorrectly disposed of down the drain can lead to chokes in the sewerage system.

It costs Sydney Water $27 million dollars to remove them and could cost you hundreds of dollars on calling out the plumber to fix blockages in your own drain.

Apart from the cost and annoyance of a blockage, it can also impact the environment so knowing what can and can't go down the drain is important.

What you can and can't pour down the sink

Milk

Milk isn't the only dairy item that can't go down the sink drain – melted ice cream and butter are also fats that can solidify in pipes.

To dispose of milk, Ben Armstrong, Sydney Water's principal manager environment, recommends it as a nutrient booster for plants.

"You can put it on your garden, pot plants. It has phosphorus and nitrogen in it which plants use so we do recommend actually doing that," he says.

The other option is to pour it into a container and put it in the bin.

Cooking oil, grease and fat

Leftover cooking oil, grease and fat definitely can't go down the sink.

These are best poured into an empty jar or container and when that's full toss it in the bin.

"If it's just cooking oil, you can store that up, I think around 20 litres and you can take that through to a community recycling center. So the New South Wales Environment Protection Authority (EPA) website gives you a list of where these recycling centers are so you can take them to be recycled," Armstrong says.

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Tea and coffee

That little bit of leftover tea or coffee in your cup is OK but large volumes with milk are best poured into a container.

Tea leaves and coffee grounds should be disposed of in your food waste bin or compost but if a few little pieces go down you don't need to worry too much.

"Small amounts of that kind of stuff you wash it up and it goes down but we suggest that, depending on the volume, we'd we'd rather you try to keep it out of the wastewater system," Armstrong says.

"It just depends the volume, really – we don't want to make it too hard for people. We understand this is probably not on their radar, and that's why we're trying to raise awareness."

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Juice

Anything with a thickness to it is best not poured down the sink as it can add to the bulk that causes blockages.

So if you have pulpy orange juice you need to dispose of find a container or empty jar and use that instead.

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Rice and noodles

We can only hope no one is pouring both of these down the drain intentionally but they can accidentally go down during the draining and rinsing process.

Ideally it's best if rice and noodles don't go down the drain as they can absorb water and potentially contribute to blockages.

"We prefer if people have a drain catcher to try and collect all the big pieces [of food]... it just helps people keep their own pipes on their property clean so they don't have to have a plumber come in and clean them out," Armstrong says.

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Dust

We've all rinsed cloths in the sink after dusting and all that dust can contribute to blockages, but we're advised not to worry too much about this one and just put the larger chunks of dust in the bin.

"It all goes back to doing little things to reduce the load collectively it has a big impact... we're not thinking that you have to try and keep all the dust out, but you do need to wash [the cloth]."

Moisture from damp absorbers

It's a question that comes to mind when trying to decide between refillable moisture absorbers and disposable ones.

If the product says the liquid in a used moisture absorber is septic safe, then you can put it down toilets regardless of whether you have a septic system.

"You'd really have to read the label and look at it, if in doubt we say put it in a plastic bag and put it in the bin," Armstrong says.

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Paint

Shockingly four per cent of people surveyed by Sydney Water believe paint is OK to pour down the drain, but it is a huge no-no.

Paint can be taken to a Paintback collection site and from there it will be transported to Paintback where the packaging is recycled and the paint itself is turned into an alternative energy source.

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