Andy Hall wrote:
I believe that they have their own fitting sizes etc. so probably not
worth doing this.

I wondered about that too, so I've carefully measured the fittings on my
Kinetico head assembly:

- The tank thread is NPSM 2 1/2 inch (nominal) with 8 threads per inch.
- The brine thread is NPT 3/8 inch (nominal) with 18 threads per inch.
- The distributor tube is 1 1/16 inch, or 27mm.

These fittings are identical to those on the Autotrol 255 and Fleck 5600
valves.

So while Kinetico manufacture a proprietary head assembly, they use
commodity components for the remainder of the unit.

This could get interesting.