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I was always told that boiling cold water in a pot is better for you then boiling warm or hot water (from the sink).

Is there any truth to this statement?

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Better in what way? –  Sam I Am Mar 26 '12 at 17:48
    
@SamIAm better to boil. easier to boil. healthier, etc. –  Neal Mar 26 '12 at 17:48
    
warm water starts to boil faster but can start with more minerals dissolved in them –  ratchet freak Mar 26 '12 at 17:50
    
Readers interested in this question might also be interested in: Is it dangerous to mix boiled and unboiled water? –  Martin Scharrer Mar 26 '12 at 17:55
    
See also When boiling water, why start from cold? on cooking.SE. –  Erik P. Mar 27 '12 at 1:34
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3 Answers

up vote 14 down vote accepted

Yes, but not for any reason related to nutrition or ease-of-boiling. Older home plumbing systems may use lead solder, and lead is a neurotoxin which is particularly harmful to children. Hot water dissolves lead more readily and stays in your home's plumbing system far longer, so it may end up with much more dissolved lead than cold water. The EPA states:

How can I reduce lead in drinking water at home?

Flush your pipes before drinking, and only use cold water for consumption. The more time water has been sitting in your home's pipes, the more lead it may contain. Anytime the water in a particular faucet has not been used for six hours or longer, "flush" your cold-water pipes by running the water until it becomes as cold as it will get. This could take as little as five to thirty seconds if there has been recent heavy water use such as showering or toilet flushing. Otherwise, it could take two minutes or longer. Your water utility will inform you if longer flushing times are needed to respond to local conditions.

Use only water from the cold-water tap for drinking, cooking, and especially for making baby formula. Hot water is likely to contain higher levels of lead. The two actions recommended above are very important to the health of your family. They will probably be effective in reducing lead levels because most of the lead in household water usually comes from the plumbing in your house, not from the local water supply.

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I had heard that cold water from the tap contains less minerals and other contaminants. The only source I found refers to lead contamination, which should be quite rare. http://www.cpsc.gov/CPSCPUB/PUBS/5056.html

If your drinking water is contaminated with lead, or you suspect that it may be, EPA recommends two immediate steps:

When the water in a particular faucet has not been used for six hours or longer, "flush" your cold water pipes by running the water until it becomes as cold as it will get.

Use only water from the cold water tap for drinking, cooking, and especially for making baby formula. Hot water is likely to contain higher levels of lead.

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How rare it is depends on the area you live and the average age of home there. If you live in a home that was built in the 70's or earlier unless you have replaced your plumbing you probably have some lead somewhere, potentially quite a bit. If you have a home built in the 90's you are probably right its pretty rare. In the 80's they really started to enforce the regs they put in place in the 70s. So It depends alot on your area and when they cracked down on the builders there. –  Chad Mar 26 '12 at 18:07
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It's also worth noting that for children, there is no safe amount of lead. Starting a boil with hot water instead of cold is pretty much a trade-off between two minutes of your time and two of your kid's brain cells. So unless you're quite certain that there's no lead in your plumbing, treat hot water as non-potable for children. –  rdhs Mar 26 '12 at 18:11
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Warm tap water might contain small amounts of lead from old pipes and should be avoided according to the following sources:

fitsugar.com: Healthy Cooking Tip: Start With Cold Water

Hot water is much more likely to leach the heavy metal from your plumbing pipes. Using lead to solder pipes wasn't banned until 1986, and unfortunately brass plumbing parts might contain a bit of lead as well. Plumbing parts legally considered lead-free today may contain up to eight percent lead. This means your chances of having lead-free plumbing are slim.

This article quotes the following recommendations by EPA (the US Environmental Protection Agency): Actions You Can Take To Reduce Lead In Drinking Water

Only Use Cold Water for Consumption
Use only water from the cold-water tap for drinking, cooking, and especially for making baby formula. Hot water is likely to contain higher levels of lead.The two actions recommended above are very important to the health of your family. They will probably be effective in reducing lead levels because most of the lead in household water usually comes from the plumbing in your house, not from the local water supply.

This was also published by the New York Times The Claim: Never Drink Hot Water From the Tap:

The reason is that hot water dissolves contaminants more quickly than cold water, and many pipes in homes contain lead that can leach into water. And lead can damage the brain and nervous system, especially in young children.
[..]
Scientists emphasize that the risk is small. But to minimize it, the E.P.A. says cold tap water should always be used for preparing baby formula, cooking and drinking. It also warns that boiling water does not remove lead but can actually increase its concentration. More information is at www.epa.gov/lead or (800) 424-5323 (LEAD).

Note that this is USA specific. Other countries might have banned lead soldered pipes much earlier or replaced such already.


See also this related question on Cooking.SE: Is hot tap water safe for cooking?.

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