I don't think you will have any problems at 220 Volts whether the water is marginally conductive or not.
I use a similar 3 fan radiator, circulating pump, flow sensor, silicone tubing etc. with distilled water and 30% antifreeze for cooling my laser tube which runs at 16,000 Volts. There are no problems (but I would not want to stick my finger, or anything else, into the water when it is running).

Tweakie.