And what about water?

For E-6 I use normal tap water as I've read here on APUG that it is better than demineralized water. In E-6 process I only use demineralized water in the stabilizer.

The instructions for the Rollei Digibase kit say that although tap water is acceptable, demineralized water is better. Normally I would blindly follow manufacturer's direction but in this case I am a bit reluctant. Maybe they say that only as a "disclaimer" in case of use of tap water which has certain undesirable characteristics. The case may be that "normal" tap water is still better than demineralized water.

Which water do you use?