The Natural Philosopher wrote:

In the UK lead free solder is specified for POTABLE water plumbing. It
has 2-5% silver in it.

If anyone has a functioning silverlight/moonlight plugin and a paid (or
free via library) membership to BSOL, they might copy and paste the
required composition from the BS EN ISO doc I referred to earlier, I'd
be willing to bet it doesn't have any silver ...