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TIL why you're not supposed to cook or drink hot tap water - it's the lead (and other heavy metals) (www.epa.gov)
submitted 1 year ago by to c/til@lemmy.ca
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Hot water dissolves lead more quickly than cold water and is therefore more likely to contain greater amounts of lead. Never use water from the hot water tap for drinking, cooking, or making baby formula.

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[–] 15 points 1 year ago (4 children)

Chemical engineer here. The difference in temperature between your cold and hot water supplies is what the problem is, and I would imagine this is not a problem at all in modern plumbing systems. Your cold water supply is usually about 50-60 deg F (10-15 C) while your hot water supply us usually set to 140 F (60 C). Solubility of some lead salts in water are given in this table with lead chloride being about 0.8 g/100mL at 10 C and 1.98 g/100mL at 60 C, so about 2.5x more soluble. The rate itself is a more complicated relationship, but it increases rapidly as well. Temperature has a big effect on these things.

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  • [–] 1 point 1 year ago* (last edited 1 year ago) (3 children)

    Okay so this might be a weird question but, what's the difference between undissolved lead and dissolved lead? Like, if there's undissolved lead in cold water isn't that still a problem? Why is it dangerous (or more dangerous) if it's dissolved?

    Clarification edit: Because you heat the water in your own home, so the lead would be still coming in through the supply, right?

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  • [–] 1 point 1 year ago (2 children)

    The difference is that solid lead stays in the pipe and doesn't get to you, the dissolution matters because the lead from the pipe dissolving is how it gets in the water in the first place. You aren't really making any lead that was already in the water worse, but a lot of people live in older houses that have lead pipes or copper pipes with lead solder. If your house doesn't have these, then it's really not an issue.

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