For many years, we have been told to boil water that may be contaminated by bacteria. Some groups have given different lengths of time that the water should be boiled. I have heard times of up to twenty minutes. Now none of this is bad advice, but it is not the best. Boiling water when it is unnecessary is a waste of fuel.
When you are boiing water you are raising the temperature to 212° F, but pasteurization only requires you to raise the temperature above 149° F. This will make a significant difference in fuel usage.
Pasteurization is quite simple. Just heat the water to just over 149° F and maintain that temperature for at least one minute. The water is considered pasteurized and safe to drink. Dr. Bob Metcalf, an emeritus professor in microbiology at California State University at Sacramento has been able to confirm this and has been involved in utilizing this technique in third world countries. This has also been confirmed by the CDC.
So if it only takes 150° F to make the water drinkable why do so many government agencies still tell you to boil water? One reason is that it takes time to educate people, including government officials to new developments. The second is that when you are boiling water, you get a visual indicator that the water has reached 212° F.
So how do you know that the water has reach a sufficient temperature to be pasteurized. One simple inexpensive method is to use a WAPI. This will tell you when your water has reached the correct temperature. It is small can fit in your pocket and is reusable thousands of times. A second idea is to have a cheap candy thermometer in your supplies.
I have been asked the question, why does it matter; it is easy to just heat the water to a boil. The reason is it takes a lot less fuel to heat water to 150° F than it does to reach 212° F. This can result in reducing your fuel consumption significantly.
Pasteurizing or boiling water is not appropriate when chemical contamination is present. This may increase your exposure to chemicals such as nitrates and solvents by concentrating them in the boiled water.
In a real emergency knowing how to pasteurize instead of boiling water may make the difference as to whether you run out of fuel.
7 thoughts on “Boiling Water Verses Pasteurization to Make Safe Drinking Water”
We boil our lake water at the cabin before using it for drinking or cooking. This is good to know. We use propane for our stove, but in the winter the top of our woodstove does the trick. – Margy
This is good info – however, here’s food for thought. Water purification is a tricky field of study. Volatile Organic Compounds (VOCs) such as solvents and agricultural pesticides, and even some life forms can “ride along” the distillation route (life forms have been found, for example, in sub-oceanic volcanic vents with extreme temperatures and pressures), and dissolved solids (salts, like magnesium and sodium chloride, for example) can make your water unpalatable, let alone somewhat toxic. Water softeners merely exchange one salt for another, “OK” if you don’t mind a lot of sodium in your drinking water. I suggest low temperature distillation and two stage filtration as a solution. The simple kitchen pressure cooker has a pressure regulator and a “vent”. As the pressure builds, the vent allows entrained air, and presumably (I would think) VOCs, to boil off and escape before the water reaches the boiling point. I’m not sure of the temperature, but somewhere around 180f the vent closes as the pressure builds. Now, think about this – if you allow the pressure regulator to vent into a distillation coil, the VOCs and any dissolved solids will be excluded and you will have, arguably, the purest water possible. If you maintain the temperature of the pot around 180f, you won’t get the roiling boil that carries impurities along in the vapor stream, and you will still save a lot of fuel. I’d like to see some scientific research on this idea, or at lest some experimental results – maybe 150f would be enough to allow distillation as water does not have to “boil” to evaporate. I saw a very good distillation unit “on the web” a while back, that was supposed to do all this – but it had a very good price as well – I would think a good “DIY” person could slap something together from the kitchen supplies that would do the job. Of course, an active carbon filter and a Sawyer Zero Point Two Filter would do the same thing (except for dissolved solids) without all the heat, fuss, and bother. Zero Point Two micron filtration excludes even viruses – and activated carbon collects the VOCs. However only distillation can remove salts and other dissolved solids – and, I would think, low temperature distillation would be best for that – we’ve all seen the chemical splatter build up around a tea-pot as the salts ride along the violent stream of steam – evaporate (at 150f?), instead of boil, the water and I would think your distillate would be as pure as possible.
Pasteurizing water seems like an interesting method to make it safe to drink. However, I can see the appeal to pasteurizing it compared to boiling water. I used to live in Taiwan where tap water isn’t considered safe to drink, so people either boiled their water, or they drank bottled water. You’re right, boiling water on a stove uses quite a bit of energy, so pasteurization methods could be beneficial for people in developing countries to help them have clean drinking water without using so much energy.
Hello! Thank you very much for having shared this information on bottling vs. purifying water. I will soon be going on a trip and and was trying to decided between both options. I think it’s good to research the pros and cons of different options to find which best suits your needs.
It’s so interesting when people who normally don’t have to think about what’s in the water they’re drinking are confronted with possible contamination. Regardless of which method is used to purify the water, I think we can learn a lot from having to consider the very real issue of unclean water people have around the world. Great article!
I understood that boiling was a great way to get clear water/purify it, but I actually didn’t think to consider that some chemicals can be concentrated in boiled water, like nitrates and solvents. That’s really good to know, and I think I’ll have to look into the method you mentioned for checking the temperature as well. Thanks for sharing on how to purify water!
Knowing how to pasteurize water will be very useful in case I’m out of clean drinking water. Heating water to just over 149 degrees seems like a good way to pasteurize water. Using a WAPI as a small thermometer seems like a helpful way to make sure that my water has reached to the correct temperature. This could be useful to make sure that my water is fully pasteurized. Thanks for the tips!