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How to stop kids' water bottles going mouldy

A thorough clean a day helps keep the germs at bay.

Last updated: 25 February 2022


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Ask any parent or carer and they'll likely agree that reusable water bottles come with having kids around. 

But while they're an environmentally-conscious way to keep our kids hydrated, what's not so thirst-quenching is the fact that water bottles (yours included!) can harbour lots of pesky germs. 

According to one study, the average water bottle has roughly six times more bacteria than a pet bowl. But before you start sending your child to school with Fido's bowl instead, check out our top tips for how to clean kids' water bottles and stop them from going mouldy. 

Choose your water bottle wisely

Try to choose a water bottle with the least amount of nooks and crannies. Not only is it the best way to avoid build-up of bacteria and other nasties, but you also won't have to sacrifice your time scrubbing awkward-shaped bottles and components. 

"Definitely look for bottles with minimal parts that are easy to clean – I recommend getting a bottle with a removable lid, plus ones with wide mouths will be easier to clean than narrow mouths," advises Dee Carter, professor in microbiology at Sydney University. 

As for material, metal is more germ-resistant than plastic.

According to one study, the average water bottle has roughly six times more bacteria than a pet bowl

"Metal bottles are better than plastic from a microbiology perspective, as metal has antimicrobial properties and is less likely to develop cracks where bacteria might be able to colonise," adds Carter. 

"However, if properly cared for, plastic bottles are fine. Just don't buy anything with antimicrobial coatings – these may contain harmful chemicals and may give a false sense of security that the bottle doesn't need to be washed."

Wash kids' bottles regularly

For something that only holds water, how dirty can a water bottle be? Answer: very! All that mouth contact and saliva is a bacteria party waiting to happen. 

"Germs can get into containers from the skin and mouth of handlers, plus from the environment," says Carter. 

"The most likely place to get a build-up is where there is contact with the mouth, but germs can also get into the water inside the bottle as there is often some exchange between water in the bottle and water in the kid's mouth."

So get into the habit of emptying and cleaning your kids' water bottles daily so you can rid them of any biofilm, a slimy substance caused by a build-up of bacteria (just like on pipes, plugs or other objects constantly in contact with water).

If washed every day, it will be easy to remove any contaminating microorganisms

Dee Carter, microbiology professor, Sydney University

"Biofilms are safe havens for microorganisms as they allow them to stick and resist being removed – washing kids' bottles is important to prevent them building up," says Carter. 

"If washed every day, it will be easy to remove any contaminating microorganisms." 


Plastic drinking bottles are not as durable as stainless steel or glass.

How to wash your water bottle

Give your kids' water bottles a thorough clean by dismantling all the parts completely and washing them in piping hot soapy water. 

You could also use a dishwasher if the bottle is dishwasher-safe, although Carter isn't a fan due to the risk of causing structural damage that "might then become a home for bacteria".

To make life easier, and to get in all those tight spots like bottlenecks, spouts and straws, it's a good idea to invest in a bottle-cleaning brush kit.

But what happens if life gets in the way and you… forget? 

"Don't panic if you miss a day or two – a good wash with hot soapy water and a scrub around the mouth of the bottle will clean it up," says Carter. "Just be sure to clean the bottle lid whenever you clean the bottle, as biofilms can also develop on this."

How to wash with vinegar

For an extra clean, consider washing with vinegar once a week.
  • For smaller bottles place in a container and cover with undiluted vinegar for 10 minutes, before rinsing washing well. 
  • For larger bottles fill with one part vinegar to four parts water, shake and leave to overnight. Discard the vinegar the next day, rinse well and allow to air dry. 

If you want extra protection you could also try store-bought sterilising solutions in liquid or tablet form to disinfect the bottle and its components. Do take care to make sure that they are safe to use for your bottle type before applying.

How to store your water bottle

If you're washing your kids' water bottles by hand, be sure to air-dry them with the lid off. Then, when it comes to putting them away, store them with the lid off or open. 

Dark, moist conditions are what bacteria loves best, so you want to ensure there isn't any residual moisture left to fester inside. Should you come across any mould or mildew on your kids' water bottle, remove all traces and then follow the sterilisation steps above.

After all, drinking water is good for you. Drinking slimy scum or (shudder) mould or mildew? Not so much.  

When to replace your water bottle

Despite the best care there will come a time when your water bottle needs to be retired. 

For plastic bottles that should be about every year, as after that they may begin to deteriorate. 

Aluminium bottles may last longer. Glass and stainless steel bottles are the most durable of all and with proper care can last for several years before they need to be replaced. 

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