I'm making a wort chiller. That's just a spiral of copper tubing to cool boiling hot beer brew to put into the fermenter. I need to join the ends, and in the configuration it's in, it would be easier to use a sweat fitting than a compression. Is there any problem with that small amount of solder regarding lead?
The last time I bought solder from a home store, it was lead free, this was over 20 years ago. I don't think you can get leaded solder unless it's for electronic use. Even that has gone to RoHS (Restriction of Hazardous Substances) in electronic manufacture to non lead as pure tin. Ignator
Yes, there would be a problem with food contact, since it's too easy to over do it and have big drips and runs of solder on the inside you can't see - but that's okay, when you go looking for plumbing solder it's ALL going to be lead-free now by law, mostly Tin with a little Silver alloyed in.
Even electronics is being forced to get rid of the lead. They're going to get burned with $1 Billion satellites dying and falling from the sky due to Tin Whiskers causing shorts on circuit boards, but the few Rocket Scientists can't out-shout the many Enviro-Nuts.
There is also Silver-Braze if you need to stay away from Tin too - that's mostly Copper and Silver. You need a little more heat, but MAPP and Air-Acetylene will get there for smaller sizes.
The problem is the heat increases the amount of lead dissolving in the brew. I remember as a kid in the early 50's my father explicitly telling me do not use the hot tap water for anything you eat or drink.
Aerospace, military and medical applications are exempt from ROHS lead free solder. They know that it's worthless shit, and that it will kill people in mission critical applications. It was the idea of idiot bureaucrats in Brussels with no science to back it up.
Was the water distilled or acidic? If not, the minerals in the water build up a layer over the walls of the pipe that covered the solder and the copper. If it didn't, the water would dissolve not only the lead, but the copper pipe.