I use RO water--no problems. RO water also takes out a huge amount of minerals etc...my water usually ends up with a ppm of about 10-15 (250 before). Most people use Cal Mag to compensate. You're using distilled water now.....what's the diff to you except for lugging at around? Wouldn't you still be using the same thing you are now if you went with a distiller and you are worried about bacteria? (Either way, use Cal Mag)