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.
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.
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).
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.)
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.
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.
All that extra lead in the tank didn’t go to a faucet. Seems better.
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.
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.
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.)
Bioavailability of lead salts (like that form when you have a lot of hot water, metallic lead, and other contaminants in a tank for a long time) is higher than of metallic lead.
Similarly, bioavailability of dissolved lead is higher than that of metallic lead particulate. The mechanism we're discussing is metallic lead particulate sitting in water heaters and dissolving.
> 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 suspect the people who say you shouldn't drink hot water have looked at the grody water that comes out when you drain a heater that's sat for a long time and see all the sediment and yuckies that accumulate at the bottom.
Every time I drain my water heater, I dumped a bunch of sediment and yuckies down the drain that otherwise would have been in me, if I were drinking from the hot side rather than the cold.
The logic you’re describing is like looking at a gross filter you’re replacing and saying “look at all this junk in the filter, I’m never filtering my drinking water again!”
Filters look gross when you replace them for the exact same reason that hot water tank is full of sediment. It removed them.
That crap usually sits in the bottom of the water heater but it can become less safe with time (e.g. forming lead salts or dissolving lead, as mentioned, or grow legionella cultures). It can also get stirred up and you can get a whole bunch more of it all at once.
It also doesn't all come from the input supply; a lot of it comes from the hot water heater itself corroding over time.