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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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[–] 20 points 1 year ago (8 children)

This seems....questionable. The entire information given is two sentences. This seems like something an eighth grader wrote for a school project.

'Hot water dissolves lead faster'. Ok, how much faster? I feel like the trip from the water heater to my sink is negligible even if I had lead pipes, which I don't.

If anyone has anything more substantial, please post it.

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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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  • [–] 15 points 1 year ago (1 child)

    When I moved into my house, I ran tests on my tap water, and found that my hot water had higher levels of iron and other metals dissolved in it. This is likely corrosion from the water heater tank. After I replaced the anode rod, the tests came out nearly identical.

    All of the levels I found were within the legal limits for human consumption, so it would've been fine... But maybe there are cases where that isn't true. The tests were very cheap, and Home Depot near me offers a 3 test kit (including lead) for free, near the water filter section. It's worth testing to be certain.

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  • [–] 2 points 1 year ago

    Also, I fucking hate that I'm saying this, I don't trust the content of .gov websites right now. The Trump administration has been mucking them up.

    I'm not saying I disagree with the claim, just that I'd try to find another reputable source for it.

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