Since having a water softener installed, some of the
Yorkshire fittings***** have a green powdery leakage.

Clearly, the nuts on the fittings need to be nipped up
again, but is the greenness indicative of a high rate of
corrosion in the system due to the salt, or is it just
a reaction to the air once it had seeped?

***** had previously fitted new taps myself; obviously
a plumber would have done it with all soldered connections
if only to make things difficult for amateur plumbers
in the future?