Andrew Mawson wrote:
[snip]

I am not suprised your kitchen tap spits after a change over, as any
air in the valve will get out that way. The cure is to tee off before
the water softener to the kitchen cold tap, and also to give the
installer a good rollocking for endangering your health.

OK. Two points.

We have an additional tap, fed pre softner, for drinking water (this
doesn't spit).
Secondly we've had the softner for five years, this problem has only
just started