Why Do Nalgene Bottles Get Cloudy? [+ How To Prevent It]

My family loves their Nalgene Bottles and so do a lot of my friends. I use mine at the climbing gym, my kids pack theirs for school, and my partner takes hers on hikes. 

A few years back, we noticed that some of our bottles were developing a cloudy film on the inside and we wanted to know why our Nalgene Bottles were getting cloudy and what we could do to prevent it. 

The most common reason Nalgene Bottles get cloudy is from mineral deposits left by hard water. Other causes include micro scratches, damage from DEET insect repellent, milk protein deposits, oxidation, and stress cracks.

The good news is, if you’re able to figure out why your Nalgene Bottle is getting cloudy, it’s usually not too hard to fix the problem and to prevent moving forward. 

It's also good to know that cloudiness does NOT mean your Nalgene isn't clean or unsafe to drink out of.

My friend had cloudy bottles and found out that they had hard water that was leaving mineral deposits on the surface of their bottles. They invested in a water softening system and haven’t had a problem since.

Where I live our water isn't very hard so we don't have this issue, but I even noticed my climbing friend's old Nalgene bottle was cloudier than my brand new one.

Hard Water Is The Most Common Cause Of Cloudy Nalgene Bottles

Hard water is water that’s high in mineral content, typically calcium and magnesium. 

While hard water is perfectly safe to drink, it often leaves a thin, cloudy film on plastic when these minerals are left behind after the water drys.

You can often see this buildup as a white residue on items like silicone ice cube trays but it can also occur on the inside of your water bottle.

At first, the buildup of minerals (sometimes called limescale) is likely to be so faint you probably won’t notice it at all.

But with repeated uses and washes with hard water over long periods of time, the layer of mineral deposits will become thicker, more obvious, and harder to remove.

This doesn't really affect the taste or quality of your water much and it's still completely safe to drink out of your Nalgene bottle but your bottle won't look as good as it does when it's transparent.

How To Prevent Hard Water Deposits On Your Nalgene Bottle

To prevent limescale buildup on your Nalgene Bottle, you need to fix the root of the issue — your home’s hard water.

You can also clean cloudy Nalgene bottles to make them transparent again.

A common misunderstanding is that any water filtration system will remove hard water minerals, but it’s simply not true. 

A basic water filtration system will make your water safer to drink and taste better, but doesn’t reduce the amount of calcium or magnesium in your water. These minerals are difficult to extract and a simple charcoal filter (or similar) won't do the job.

Water softening systems, on the other hand, like this one by Aquasure, will soften the water in your home and, as a result, reduce or eliminate mineral deposits on plastics completely.

Reverse osmosis water filters and ultrafiltration systems are types of premium water filters that are also able to soften water, but aren’t specifically meant to do so and aren’t as effective as a result. 

Ultimately, the cost and effort to install a water softening system or premium water filter is a little steep if your only concern is keeping your Nalgene Bottle crystal clear.

But there are many other benefits to eliminating hard water in your home — your appliances will last longer, your skin and hair will be healthier, it may improve digestive health, and your water will taste better. 

If you don’t want to invest in a water softening system, there are several DIY solutions to remove mineral deposits from your Nalgene Bottle, including soaking it in diluted vinegar or bleach, scrubbing with baking soda, or using ice and salt. 

Other Causes Of A Cloudy Nalgene Bottle

Not every cloudy Nalgene Bottle is the result of hard water stains — micro scratches, damage from a DEET-based insect repellent, or aging may be to blame.

As I mentioned before we don't really have hard water issues where I live but if you compare my friend's 15+ year old Nalgene bottle to my brand new one you can see that here's is cloudier than mine.

Considering the age of her bottle it's actually holding up really well. I've seen other people's Nalgene bottles that are WAY cloudier than this.

So what's causing this cloudiness exactly?

Micro Scratches On The Bottle’s Surface

Older bottles and bottles that have lived a hard life will collect tiny surface scratches on the bottle’s exterior that may eventually make the bottle less transparent.

If you clean the inside of your bottle with a rough bottle brush, micro scratches will begin to accumulate on the inside of your bottle as well.

I use a soft bottle brush to clean my Nalgene to prevent this exact problem.

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03/06/2024 07:52 pm GMT

Damage From A DEET-Based Insect Repellent 

As this Redditor learned, DEET is great at keeping bugs away but will damage plastic if it makes contact.

If you’re taking your Nalgene camping or backpacking, consider using a DEET-free insect repellent instead. 

Permethrin and Picaridin based sprays won’t damage your Nalgene Bottle and are just as effective at keeping bugs away. 

Milk Protein 

Certain fats and proteins will cling to plastic bottles. 

If you’re using your bottle for shakes or smoothies containing whey or casein protein, that cloudy film on the inside of your bottle may be the result.

You may not be washing the bottle often enough or thoroughly enough. 

An Aging Bottle

And lastly, your Nalgene Bottle may just be getting cloudy because it’s really old. I suspect this is the issue with my friend's bottle. Though I do wonder whether it not it could be cleaned up and made to look transparent again. Click here for the guide on how to clean a cloudy Nalgene bottle.

Age-related damage, like stress cracks and oxidation will slowly develop over time. 

If you’ve had your bottle for what feels like forever, and it’s spent a lot of time in the sun or heat, it may just be time for a new bottle.

It couldn’t hurt to see if the damaged bottle is covered by Nalgene’s lifetime warranty