
Boiling water in PET bottles - Does that really work?
👉 The key facts from this guide
- The PET bottle method is an emergency technique for boiling water by holding a plastic bottle over embers – thanks to the high melting temperature of PET, this works.
- Here’s how it works: Fill the bottle to 80%, hold it without a cap over the embers, wait for bubble formation, continue heating for 1–2 minutes, then let it cool down.
- Ideal for absolute emergencies to disinfect water when no other options are available – better to risk microplastics than to drink contaminated water and get sick.
- The method carries risks: one-time use is okay, but do not reuse, as chemicals might be released – thicker bottles are more stable.
- Compare water purification methods: boiling kills pathogens but does not remove chemicals; filtering clarifies water but might overlook viruses.
- Note: The combination of filtering and boiling is the safest method – plan well, emergencies can happen, and this knowledge can save lives.
The headline sounds totally crazy at first, right?
When I read this in several survival books, I could hardly believe it.
I just had to try it myself – and it actually works!
The water tasted completely normal, without any plastic taste at all.
This is how the emergency method works
The reason it works at all: PET melts only at about 260 °C, while water boils at 100 °C. This gives us a safe temperature window.
The steps:
- Fill the bottle to about 80% (the bottle shrinks when heated)
- Place the bottle without a cap about 12–15 cm above the embers – it can also be placed in the embers
- Wait for bubbles to rise (this may take some time)
- Continue heating for about 1–2 minutes
- Let it cool down
Here is the appropriate short video for that (in German):
Pro tip: Filling the bottle almost completely (80%) is ideal! The less air there is in the bottle, the less the plastic deforms. This makes the whole method safer and easier.
Risks and Considerations in an Emergency
I can already imagine what your concerns about the method might be:
Doesn't microplastic get into the water?
Yes, indeed that can happen (but I did not have the water tested). Nevertheless, I would like to clearly list the advantages and disadvantages of the method here:
The problem with untreated water:
- Severe diarrhea and vomiting
- Extreme fluid loss
- Quickly life-threatening in the wild
- Critical without medical assistance
The PET method:
- Yes, some plastic could leach into the water
- One-time consumption is less dangerous than contaminated water
- Only suitable for real emergencies
The fact is: The risk of some microplastics is lower than dying from contaminated water.

The same bottle should not be reused multiple times, as more chemicals may be released with each heating. Thinner bottles also work, but thicker ones last longer.
Important to know: Important: This is an absolute emergency method — for example, when you need to disinfect a wound or are threatened by dehydration. It is not suitable for normal use. Instead, always carry a small stainless-steel cup or a stainless-steel bottle (without BPA coating) with you.
Comparison of Water Treatment Methods
I would like to give you a brief overview of the water treatment methods. This way, you can see which methods are ideal and what they are useful for:
Method | Removes bacteria | Removes viruses | Removes heavy metals | Removes chemicals | Special features |
---|---|---|---|---|---|
Boiling | Yes | Yes | No | No | Energy-intensive, but very safe |
Homemade filter | No | No | No | No | Depends on filter quality |
Water filter (industrially manufactured) | depending on product | depending on product | No | No | Depending on pore size, may also remove viruses or bacteria |
Distillation | Yes | Yes | Yes | Mostly | Very complex, but the safest |
UV light | Yes | Yes | No | No | Requires clear water and takes a long time |
Boiling (Water Disinfection) vs. Filtering (Water Purification)
Boiling:
- Reliably kills all pathogens
- Works even in very cloudy water
- Only needs heat and a heat-resistant container
- Does not remove heavy metals or chemicals
Filter:
- Filters suspended solids and larger particles
- Some filters also remove heavy metals
- Viruses are often too small for normal filters
- Filters can clog or fail
Note: The safest method is the combination of filters (for suspended particles) and subsequent boiling (for pathogens).

Read also
How to build your own survival water filter [Survival Basics] – You will learn how to build a simple water filter yourself. I will also show you two more filters that are easy to implement outdoors.
Last Words on Emergency
It is clear: The PET bottle method is not ideal. But when you are outside, your water is all gone, and you only have a plastic bottle – then boiled water is definitely better than contaminated water to drink.

For the future: Plan your tours well. Bring enough water. But also know: Sometimes you find yourself in unforeseen situations. Then this knowledge is worth its weight in gold.
Here you will find more references to read up on:
- Finding, collecting, filtering, and making drinking water – the ultimate water guide
- Survival time without water: How long can the body last without fluids?
- The 11 best outdoor water filters 2025 for clean drinking water while camping
- Boiling water without a pot: These 8 methods will help you get drinkable water
- Can drinking saltwater or seawater make you sick or even kill you?
And if you want to test your knowledge, then check out the Water Survival Quiz.
What do you think – surprising that it really works?
PS: In my test, the water tasted completely normal, by the way. No plastic taste, no change – just completely normal boiled water.

Sources for the guide
Survival Basics: 365 Überlebenstechniken für den Ernstfall Taschenbuch – 27. April 2018 von Creek Stewart (Autor)
https://www.srlongroup.com/can-you-put-boiling-water-in-a-pet-bottle/
https://willowhavenoutdoor.com/someones-trash-could-save-your-life-how-to-boil-purify-water-in-a-plastic-bottle/

Author of the guide
Martin Gebhardt
Hey, I'm Martin. On my blog, you will learn the basics and numerous details about living in the wild. I think survival, bushcraft and the good life in nature are the keys to happiness. Find me here on Instagram or on YouTube. You can find more about my mission on the About Me page.
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