[edwardyeeks]

Nepenthes actually tolerate tap water very well. As strath has mentioned, mineral buildup especially salt can harm the plant long term and increases the neccessity to repot the plant. In fact, the entire pot of the nepenthes should be flushed with water every time watering is needed. Water must be allowed to drain off through the bottom of the pot. This should wash off some minerals and salt in the media and keep the media's mineral level low. Your nepenthes media choice will also affect the mineral build up. Note that this is the general watering technique for all nepenthes. There are a few species which are rather fussy about their watering and their media.

To give you an idea, nepenthes grow in the wild tropical jungles where there are very low, but considerably higher level of mineral contents in their soil compared to the native swamps of the VFTs and Sarracenia. Because of this, neps tend to tolerate mineral build up much better compared to other CPs. Also, they shown obvious signs when mineral build up is too much for their roots to handle. The pitchers usually shrink and deform or they do not form. Hope all of this helps.