Water

Nepenthes in nature receive most of their nutrients through the digestion of insects (occasionally small mammals) in their pitchers, and from light. When too many minerals are in the water you give to your plants it can cause adverse reactions or even death. It is advised to use distilled water, rain water, or water that has gone through reverse osmosis. This doesn't necessarily mean you can't use your tap water. If you want to use your tap water make sure the chlorine level is less than 5 ppm and the water hardness is below 100-150 ppm. If your water is harder than this and you can't use the other water sources mentioned then you will need to change your soil at least once a year (but I wouldn't do it more than three times as it will traumatize your plant being handled/transplanted that often) to remove the build up of minerals. If you have harder water and you are forced to use it as your primary water source you can also do an occasional "flush" with rain/distilled water to try to move some of the minerals out of the soil, although you will still need to re-pot your plant about once a year.