I was at a friends place a few weeks back when he set his up. IIRC I read in the instructions that they prefer distilled but say you can use tap water. On their web site FAQ, they say...
"While you can use tap water in cases where distilled water may not be available to you, tap water often contains minerals or other impurities that may be deposited in the grooves of your record, undermining the cleaning effectiveness of the brushes and fluid. In addition, these tap water impurities may become deposited on the brushes, further hampering the effectiveness of future cleanings."
Not sure how much of the undesirable minerals the filter will have removed.
