5 ms·

If it’s a lead trap… wouldn’t that mean the water that comes out has less lead in it than the water that goes in? Assuming the water going into the heater is th

If it’s a lead trap… wouldn’t that mean the water that comes out has less lead in it than the water that goes in? Assuming the water going into the heater is the same as the water coming out of your cold tap.

throwaway89201 3y ago
No, the article states that lead particles from upstream get trapped inside the water heater, which then gradually dissolve, especially when left stagnant overnight.
- mattmaroon 3y ago
  Right but all those particles just end up in your glass in the cold water supply right? Better they get trapped in heater.
  - anonymouskimmer 3y ago
    Whether or not it's a good idea would really depend on what percentage of hot versus cold water ends up consumed (versus used for non-consumption purposes). Over the lifetime of the undissolved lead accumulation.
  - adrianN 3y ago
    I believe elemental lead is not terrible when ingested, but lead ions are much worse.
    - Paul-Craft 3y ago
      Yeah, metallic lead is pretty safe to handle overall, as long as you don't inhale the dust. I wouldn't want to go trying to ingest it, but the amount of incidental exposure you'd get from handling, say, a lead brick at room temperature, is not much of a worry. Wash your hands after handling it, wear proper PPE, and you should be fine. Edit: this isn't counting stuff like using lead solder. In that case, ventilate the crap out of your work area (preferably doing the work under a hood), wear PPE, and clean any equipment used.
      - exmadscientist 3y ago
        Leaded solder is no more dangerous than lead bricks. The lead never vaporizes (look up the boiling point of lead if you don't believe me), so the same hazards of skin contact and lead dust are the relevant ones. And lead dust is less of a problem for solder because of the alloys used being a lot less prone to making dust than lead bricks (source: extensive personal experience with both). The fluxes used in solder are far more dangerous than any lead. However, carefully washing one's hands only goes so far. Your work area will still be covered in small amounts of lead residue just from all the transfer via tools and fingertips. It is very reasonable to avoid leaded solder entirely these days in favor of newer alloys like SN100C, which have performance very close to Sn63Pb37 (though not the same).
        sokoloff 3y ago
        I’ve switched to lead-free solders for all new work, but still do any repair/rework of old products with leaded solder as I’ve never found a lead-free solder that works well (plus, I’ve now got 5 lifetimes’ worth of leaded solder supplies). Have you found any that work well in repairs/cross-contamination cases? I suspect a lot of the early complaints about lead-free solder being a dire problem functionally were from people using the wrong temp or cross-contaminated tools. (I use a cheaper segregated station for leaded as I got tired of changing tips on the nicer station.)
        exmadscientist 3y ago
        ...honestly we play pretty fast and loose with mixing alloys around here. We really shouldn't since it can be very bad, as you know. The three RoHS alloys I have experience with are SAC305 (blech, no idea why people tolerate this stuff), SN100C (seems to be great on new assemblies, never much tried mixing it), and REL22 from AIM (this is on our "high strength" spool holder, next to the Sn62Pb36Ag2 silver solder, so people tend to graduate toward it for no better reason) which seems to do pretty well in typical lab conditions after being used to rework either SAC305 or SnPb joints. We don't do real testing around here. When I am knowingly mixing alloys I will try to clear or flood the joint or both (remove as much old solder as possible with braid, or add new solder in excess). We are pretty good around here about using Way Too Much flux, which is of course the correct amount. This might help. Either way we seem to do okay for this light use.
lovelyviking 3y ago
“The flushing helped significantly in almost every case. Among water heaters where water levels first tested above 50 ppb, flushing dropped the lead levels on average from 456 ppb to 20 ppb” They took samples from the tank as I understand before and after flushing. If it’s in the sample some of it presumably goes to the water you use.
- mattmaroon 3y ago
  Right so the hot water tank was trapping lead that, in your cold supply, just passed right through to your faucet. All that extra lead in the tank didn’t go to a faucet. Seems better.
  - mlyle 3y ago
    Of course, it's complicated because the pre-dissolved lead and lead that's formed into salts, etc, is more bioavailable and less likely to pass through you. Presumably the water heater reaches equilibrium and doesn't remove lead forever-- you get equal rates of lead in and lead out. But the water heater may be making the lead more bioavailable.
    - mattmaroon 3y ago
      Perhaps. Or perhaps hot water picks up more leas from copper pipe solder out whatever downstream. That’s why this is a really dumb testing method considering a good one (just testing at the faucet) would have been as easy to do.
      - mlyle 3y ago
        Testing at the faucet is definitely going to end up identical in concentration (plus whatever it picks up in pipes in the house), but not necessarily bioavailability.
        mattmaroon 3y ago
        I can’t find anything indicating there’s any difference in bioavailability between hot and cold water, or that it’s a concern at all. I’d just assume whichever has less lead in it is what I’d rather drink. If the hot water tank is removing lead from the supply and trapping it, I think I’d rather use it for cooking. (Of course I’m not trying to drink warm water out of the tap in any case. ) And in any case what this study is measuring seems to have little relation to what you actually want you know. But I’d guess you’re right, the hot water tank is probably removing some lead (hence the higher concentration) but not enough to matter much. I strongly suspect the people who say you shouldn’t drink hot water are just parroting something that may be entirely mumbo jumbo, or may be true in some instances for homes with older plumbing but not anymore. I’ve replaced all the plumbing between the street and my kitchen with Pex so there’s no solder after the water heater. (Perhaps hot water does dissolve more lead from that, though I still have a hard time believing it is significant.)

throwaway89201 3y ago

No, the article states that lead particles from upstream get trapped inside the water heater, which then gradually dissolve, especially when left stagnant overnight.

mattmaroon 3y ago
Right but all those particles just end up in your glass in the cold water supply right? Better they get trapped in heater.
- anonymouskimmer 3y ago
  Whether or not it's a good idea would really depend on what percentage of hot versus cold water ends up consumed (versus used for non-consumption purposes). Over the lifetime of the undissolved lead accumulation.
- adrianN 3y ago
  I believe elemental lead is not terrible when ingested, but lead ions are much worse.
  - Paul-Craft 3y ago
    Yeah, metallic lead is pretty safe to handle overall, as long as you don't inhale the dust. I wouldn't want to go trying to ingest it, but the amount of incidental exposure you'd get from handling, say, a lead brick at room temperature, is not much of a worry. Wash your hands after handling it, wear proper PPE, and you should be fine. Edit: this isn't counting stuff like using lead solder. In that case, ventilate the crap out of your work area (preferably doing the work under a hood), wear PPE, and clean any equipment used.
    - exmadscientist 3y ago
      Leaded solder is no more dangerous than lead bricks. The lead never vaporizes (look up the boiling point of lead if you don't believe me), so the same hazards of skin contact and lead dust are the relevant ones. And lead dust is less of a problem for solder because of the alloys used being a lot less prone to making dust than lead bricks (source: extensive personal experience with both). The fluxes used in solder are far more dangerous than any lead. However, carefully washing one's hands only goes so far. Your work area will still be covered in small amounts of lead residue just from all the transfer via tools and fingertips. It is very reasonable to avoid leaded solder entirely these days in favor of newer alloys like SN100C, which have performance very close to Sn63Pb37 (though not the same).
      - sokoloff 3y ago
        I’ve switched to lead-free solders for all new work, but still do any repair/rework of old products with leaded solder as I’ve never found a lead-free solder that works well (plus, I’ve now got 5 lifetimes’ worth of leaded solder supplies). Have you found any that work well in repairs/cross-contamination cases? I suspect a lot of the early complaints about lead-free solder being a dire problem functionally were from people using the wrong temp or cross-contaminated tools. (I use a cheaper segregated station for leaded as I got tired of changing tips on the nicer station.)
        exmadscientist 3y ago
        ...honestly we play pretty fast and loose with mixing alloys around here. We really shouldn't since it can be very bad, as you know. The three RoHS alloys I have experience with are SAC305 (blech, no idea why people tolerate this stuff), SN100C (seems to be great on new assemblies, never much tried mixing it), and REL22 from AIM (this is on our "high strength" spool holder, next to the Sn62Pb36Ag2 silver solder, so people tend to graduate toward it for no better reason) which seems to do pretty well in typical lab conditions after being used to rework either SAC305 or SnPb joints. We don't do real testing around here. When I am knowingly mixing alloys I will try to clear or flood the joint or both (remove as much old solder as possible with braid, or add new solder in excess). We are pretty good around here about using Way Too Much flux, which is of course the correct amount. This might help. Either way we seem to do okay for this light use.

lovelyviking 3y ago

“The flushing helped significantly in almost every case. Among water heaters where water levels first tested above 50 ppb, flushing dropped the lead levels on average from 456 ppb to 20 ppb” They took samples from the tank as I understand before and after flushing. If it’s in the sample some of it presumably goes to the water you use.

mattmaroon 3y ago
Right so the hot water tank was trapping lead that, in your cold supply, just passed right through to your faucet. All that extra lead in the tank didn’t go to a faucet. Seems better.
- mlyle 3y ago
  Of course, it's complicated because the pre-dissolved lead and lead that's formed into salts, etc, is more bioavailable and less likely to pass through you. Presumably the water heater reaches equilibrium and doesn't remove lead forever-- you get equal rates of lead in and lead out. But the water heater may be making the lead more bioavailable.
  - mattmaroon 3y ago
    Perhaps. Or perhaps hot water picks up more leas from copper pipe solder out whatever downstream. That’s why this is a really dumb testing method considering a good one (just testing at the faucet) would have been as easy to do.
    - mlyle 3y ago
      Testing at the faucet is definitely going to end up identical in concentration (plus whatever it picks up in pipes in the house), but not necessarily bioavailability.
      - mattmaroon 3y ago
        I can’t find anything indicating there’s any difference in bioavailability between hot and cold water, or that it’s a concern at all. I’d just assume whichever has less lead in it is what I’d rather drink. If the hot water tank is removing lead from the supply and trapping it, I think I’d rather use it for cooking. (Of course I’m not trying to drink warm water out of the tap in any case. ) And in any case what this study is measuring seems to have little relation to what you actually want you know. But I’d guess you’re right, the hot water tank is probably removing some lead (hence the higher concentration) but not enough to matter much. I strongly suspect the people who say you shouldn’t drink hot water are just parroting something that may be entirely mumbo jumbo, or may be true in some instances for homes with older plumbing but not anymore. I’ve replaced all the plumbing between the street and my kitchen with Pex so there’s no solder after the water heater. (Perhaps hot water does dissolve more lead from that, though I still have a hard time believing it is significant.)