Can I water phragmipediums and paphiopedilums with only distilled water? My greenhouse is full of carnivorous plants and Sphagnum moss, which require distilled water, and water often gets splashed around and drains down into other lower plants.
Do they need lots of nutrients, like from tap water? Or is distilled fine if I fertilize?
Distilled is always a better option for orchids. You can always add what they need. Paphs can handle hard water, but no plant likes chlorine or road salt.
No. My phrags and paphs all get very hard water but I allow it to drain out of the pot. Some paphs like P. niveum live in limestone. I have a 15 year old which is potted in peat with limestone chunks and has bloomed repeatedly. My phrag (uranus) has always been kept constantly moist but paphs can get completely dry for days and survive, at least the species I have encountered. There is even a species of Mexican cypripedium which is a genuine xerophyte.