“Purified” is a bit of a general term, so let me break apart the potential issues: 1) Distilled water shouldn’t be a problem. 2) Reverse osmosis filtered water may or may not be a problem depending on the water source. Some dissolved minerals could conceivably get through, and minerals are generally going to be ionic. 3) Ionic contamination along with moisture and current can lead to dendritic growth. DI rinse at the end of the cleaning cycle could reduce this risk. 4) Contamination could lead to increased foaming.