News

May 22, 2024

How often do you need to wash your water bottle? It depends on the material

By Rachel Rasker You wash your glasses and your mugs all the time, but how often do you wash your water bottle? Many of us sip from the same one day in and day out, with Gen Z becoming so close to

By Rachel Rasker

You wash your glasses and your mugs all the time, but how often do you wash your water bottle?

Many of us sip from the same one day in and day out, with Gen Z becoming so close to their flasks, they've coined the term "emotional support bottle".

I'm guilty of rarely – if ever – washing my water bottles. Surely a quick rinse every now and then is enough, right? It's just water.

I asked the experts whether I'm a grub or a genius.

For Anas Ghadouani, a Professor of Environmental Engineering at the University of Western Australia specialising in water resources, the question of how often you should wash your water bottle comes down to your standards.

It is worth taking extra care with certain foods that are more likely to harbour nasty pathogens.

He says you're unlikely to get sick from an unwashed bottle, so you don't technically "need" to clean them.

"It all depends on your feeling of cleanliness.

"If I took a swab from my water bottle, you'd see some growth, some bacteria.

"If I looked at that I'd go: 'Wow, that's beautiful.' But somebody else may look at that and go: 'That's gross.'"

While Lydia Buchtmann from the Food Safety Information Council agrees it isn't a "huge risk", she says there is a possibility of developing gastro or food poisoning from a dirty water bottle, which is why she recommends washing them daily.

Dee Carter, a Professor in Microbiology at the University of Sydney, compares it to leaving a cup by the bathroom sink – after a while, it starts to get a bit gunky.

"The same thing is happening on the inside of a water bottle – you'll start to get that slimy build-up.

"I think we all want to practise good hygiene. And it's probably not desirable to be drinking something that hasn't been cleaned for a long time."

After weeks without washing, there will be growth inside your water bottle, but Professor Ghadouani says most bacteria and microorganisms live "in perfect harmony with us, including inside our body".

How much water should we drink every day? And what if it doesn't have to be eight cups?

While some bacteria – known as pathogens – can make us sick, he says it's improbable a pathogen will make it into your water bottle, because the source of our water in Australia is safe and chlorinated.

Professor Carter says mould can develop on the dark, damp insides of water bottles, and around their spouts.

"That can be a problem because sometimes moulds make toxins that you really don't want to be ingesting."

Ms Buchtmann says while food poisoning from water bottles is not a "big issue" in Australia, your risk of illness is increased if you're sharing a bottle, or if kids are passing theirs around at daycare.

Bacteria and pathogens are also more likely to grow in heat – so if your bottle's out in the sun all day, or you leave it in a hot car, a wash might be a good idea.

Professor Carter doesn't recommend plastic bottles – reusable or otherwise.

"They start to get that kind of plasticky flavour over time, and that's because stuff is leaching out of the plastic into the water – probably not stuff you really want to be drinking."

This is still the case if they're BPA-free. Instead, she suggests using metal or glass bottles.

However, Professor Ghadouani says that not all metal bottles are equal – your best option is food-grade stainless steel.

"It washes well and doesn't grow stuff. Only problem is that it's bloody expensive.

"If you pay $2 for a metal bottle, it's not good metal. Good metal is expensive."

Bottles with wide mouths and removable lids are going to be easier to clean. Additionally, it's best to avoid ones with crevices and craters, as this is where you're most likely to see growth – and these areas could prove tricky to clean.

Professor Carter aims to wash her bottles daily. But she admits she sometimes forgets about washing the bottle beside her bed.

Professor Ghadouani's "obsessions" are the cleanliness of his keyboard and phone screen, and he isn't too bothered about his bottle – but he still washes it every few weeks.

To wash it properly, he's a big fan of a bottle brush so you can properly get to all the corners. Or if your bottle's mouth is wide enough, you may be able to use a normal dish brush.

Use soap and warm water, and leave it on a rack to properly dry out overnight.

Ms Buchtmann says to pay particular attention to the mouth and lid of your bottle when cleaning, and that you should be completely emptying and refilling your bottle at the end of the day, rather than just topping them up.

If your bottle is plastic, Professor Carter warns against using hot water from the kettle or putting it in the dishwasher, as this intense heat could cause it to degrade, and you could end up with microplastics coming out.

Not that she is recommending the use and throwing away of disposable plastic bottles.

"The last thing I want is for people to freak out thinking there's a problem with reusing a bottle. There isn't, it's just best to look after it properly."

Plus, there's nothing more comforting than an emotional support bottle.

Get our newsletter for the best of ABC Everyday each week