We also only use demineralised water. With a little detergent recommended for robot mops.

I only use tap water. I don't think distilled water is even recommended. But I'm not sure.

Yes, you can use tap water. But I clearly recommend filtered water, I use my Br** filter for this. That way the robot and the station simply last longer, the thing is expensive enough.

i have another increase, i use distilled water. i want to imagine what it will look like in a year. and how the descaling works is also questionable. one thing is not to use cleaning agents in the tank.