It's been quite a few years since I had to buy any flux and, looking online today, there now seems to be a new (to me) version called 'lead free solder flux'. What's changed?
I only need it for some fittings on the central heating system and hot and cold water pipes to a basin.
Lead solder has been outlawed for potable water supplies. In effect, no-one (professionally) uses lead any more, even on gas pipes which can be lead soldered. Non-lead solder needs a slightly higher temperature, so the flux has to cope with those temps. It may well be marketing speak saying it is 'non-lead' flux, as they are the same thing afaiaa.
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