On Nov 17, 9:10 am, wrote:
Just put in a water softener brought from Screwfix 4 years ago
(that's good going for my DIY jobs ! )

Where do you get your salt from?

Costco.

Needs granular salt apparently
So does my Bosch dishwasher, I think.
I've fed it on the tablets I use in the water softener, with no ill
effects, as yet (5 or 6 years).

Salt is salt. In reality, it uses a brine solution and I can't see how
the shape of the solid salt will affect operation.
Anyone saying otherwise is usually in marketing.