Scientists explain whether it is safe to boil water again

Boiling water before drinking is a necessity to kill any bacteria and germs that may be present in the liquid. However, is it possible to re-boil water?

ScienceNotes reports on the chemical and physical properties of water that has been boiled again.

What happens when you boil water

When you boil pure water, its chemical composition remains the same. No matter how many times you boil it, you have pure water.

Repeatedly boiling drinking, mineral and spring water changes its chemical composition because the water contains other compounds. This is because when you boil water, some of it is lost to the atmosphere as steam, concentrating the remaining chemicals. This does not pose a health risk, although repeatedly boiling hard water can lead to the formation of chalky white scale inside the kettle and water heater.

Read also: Is it safe to drink water that has been boiled repeatedly

Limescale is mainly made up of calcium carbonate (CaCO 3), magnesium hydroxide (Mg(OH) 2) and calcium sulphate (CaSO 4). Most people believe that these minerals improve the taste of water and make it healthier. However, repeatedly boiling water with a high calcium content (hard water and mineral water) can be dangerous for people with gallstones, kidney stones, arthritis or atherosclerosis.

Does repeatedly boiled water cause cancer?

Drinking boiled drinking water does not cause cancer. However, it can increase the risk of cancer (due to pesticides and other chemicals), methemoglobinaemia (due to nitrates in fertilisers) and arsenic toxicity (arsenic, natural or from waste). Lead is also concentrated during repeated boiling.

If you use well water or are concerned about lead in your water supply, you can have your water tested. Keep in mind that repeated boiling does not significantly increase the concentration of undesirable chemicals that are already in the water. Contaminated source water should be filtered once before boiling, rarely twice. Uncontaminated water is safe to boil and re-boil.

The main danger of boiled water

One of the real health risks associated with repeatedly boiling water is that it can overheat and create a scalding hazard. Repeatedly boiling water removes dissolved gases from the water, making it "flat". Overheating can occur, making the water hotter than its normal boiling point, causing it to "explode". For this reason, it is not a good idea to re-boil water, for example, in the microwave.

Read also: Why you should not squeeze the contents of a tea bag into a mug and brew tea for a long time

Repeatedly boiling water can affect the taste

This is because fresh water contains many tiny air bubbles. When you heat the water, the dissolved gases slightly increase the acidity of the water, allowing for better extraction of flavour molecules. Some people also claim that boiled water has an unpleasant taste. Therefore, it is best to brew coffee or tea with boiled fresh cold water.

Earlier, we wrote about what not to do so that lemon tea does not lose its beneficial properties, as well as what 3 spices are added to tea to make it more healthy.

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