The Truth Behind Reboiling Water: Is It Safe To Twice Boil Water?

I’ll be the first to admit it, I’m LAZY A.F. when it comes to my tea drinking habits! If there’s a way to get my tea fix faster, I’ll always opt for it. So if there’s leftover water in the kettle, why dump it out? Just reboil it! But then I realized, is it safe to reboil water?

There are so many contradicting articles about reboiling water. One source would say that is was toxic, while the next one said we had nothing to worry about!  So here are both sides to the story – why do some people think it’s toxic to twice boil water, and others don’t, and is it potentially better to boil water…?

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Is It Safe To Reboil Water? All your questions about twice-boiled water are answered! #twiceboiledwater #reboilingwater #reboilingwatertoxic #safetwiceboilwater

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Quick Disclaimer!

I am neither a scientist nor medical professional! I simply researched this topic out of my own curiosity to find out if I can continue in my lazy ways of reboiling water. Plus, once I found out the truth, I wanted to share it with you in an easy-to-read format. I researched both sides of why it’s safe to reboil water, and why it might be considered toxic.

You can find all the sources I used throughout this post.


Is It Safe To Reboil Water?

Boiling water twice is way faster than refilling my kettle with cold water and waiting for it to boil again. So I looked into whether or not it’s safe to reboil water or if boiling water twice turns the water toxic…

At the end of the day, the safety of reboiling water comes down to the quality of the water you’re using before it’s even boiled. If your water is safe to drink before boiling it, it should be safe to boil it more than once. There is a chemical build up that happens the more time water is reboiled, but it’s very minimal.


Why Can It Be Bad To Boil Water Twice?

The claim is that when you reboil water, it changes the chemicals to become toxic.
Hm… this sounds kind of familiar… kind of like the claim that adding honey to tea turns it toxic too. Find out the truth behind that claim.
The science behind water becoming toxic is routed in theories of concentration and evaporation. It’s believed that once you boil water, some of the water evaporates, leaving a higher concentration of bad chemicals behind. Essentially, when you boil water, you’re left with less water, and more chemicals… does that make sense?
Read more about that theory.

adding honey to your tea toxic
You might also be interested in reading…

Is Adding Honey To Your Tea Toxic?


Harmful Chemicals Found In Twice Boiled Water

The chemicals people are primarily worried about in twice boiled water are nitrates, arsenic and fluorides. 

Nitrates, a.k.a nitrogen is most commonly found in water. It has been linked to cancers such as leukemia and lymphoma.  

Arsenics can occur naturally, they’re primarily from farms, or industrial waste. These are more of a concern if you’re living in a rural area. But arsenic can also be linked to certain cancers, heart disease, infertility, and even neurological problems.

I’ve only heard about fluoride at the dentist, but it can also have harmful affects on our body. There’s a claim that too much fluoride in our water can lead to kidney disease, bone cancer, and arthritis. It’s even linked to a lower IQ in children, as it hinders their cognitive and neurological development.

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The Reality: It’s About the Quality Of Your Water Before Boiling!

The reality is that these harmful chemicals found in our water do become more concentrated the more times you boil your water. But! and there’s always a but! The amounts are so small, that they’re negligible. Water should never contain large quantities of nitrates, arsenics and fluoride to begin with. 

Water supplies in cities should be monitored to control the levels of these harmful chemicals. So even if you’re getting your water from the tap, it should be safe to drink.

For example, nitrates are most commonly found in underground water sources, or in fertilizers. This is not going to be in your city tap water. If you’re boiling water with high levels of these chemicals, your issue isn’t from twice boiling your water. In fact, when we boil water the chemicals change for the better…

Boiling Water Makes It Safer To Drink…

Our water becomes safer for us to drink after it’s boiled because it kills off any nasty bacteria or germs that might be in the water.

Most of us are not boiling filtered water exactly for this reason – we simply don’t need to. Anything unwanted in our tap water, will be boiled out. 

So it’s all about the quality of your water before it was ever boiled in the first place. If you’re concerned, I recommend testing your water first.  

Source: Read more about how it’s all about the quality of your water.


Reboiling Water More About Taste Than Toxicity?

A study found that reboiling water was more about taste than toxicity. This also may have more of an affect your cup of tea rather than coffee. 

The theory stems from the fact that boiling water removes the oxygen. Apparently, deoxygenated water can taste more flat… although I’ve never noticed any difference. Read more.  


What Should You Do – Is It Safe To Reboil Water?

So to reboil, or not to reboil? That is the question.
As much as I want to say it’s more about taste than toxicity, if you want to stay on the safe side, boil fresh water every time. Let’s be real, does it really take that much longer?
If you are in a rush though, or just want to top off your tea, there really isn’t much risk associated in reboiling water at least once.
I’ve also started boiling less water, this way it forces me to refill my kettle every time I need to top off my tea.

My Favourite Kettle To Reboil Water

Make reboiling EVEN EASIER with the Cuisinart CPK-17 PerfectTemp 1.7 L Electric Kettle. It keeps the water at the right temperature for you for 30 MINUTES!

It’s my absolute favourite kitchen appliance! I can boil my water at different temperatures depending on the type of tea or coffee I’m making. Then it will keep reboiling the water every few minutes to keep the right temperature. That means I can refill my tea all morning long and sleep easier at night knowing it’s safe to reboil water! You can order it on Amazon, see updated prices (shopping in Canada?).

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More Sources

Is Reboiling Water Safe? 

Is Twice Boiling Water Toxic?

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Is It Safe To Reboil Water? All your questions about twice-boiled water are answered! #twiceboiledwater #reboilingwater #reboilingwatertoxic #safetwiceboilwater
Is It Safe To Reboil Water? All your questions about twice-boiled water are answered! #twiceboiledwater #reboilingwater #reboilingwatertoxic #safetwiceboilwater


  1. Yeah! by reboiling the water, you might lose 2-4% of water which is insignificant. There is no way it can harm you like leftover toxic from small amount evaporated water make you sick. I’m looking for it cuz my mom always tell me reboiling water is so bad 🙂

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