Unless you absolutely have to cut the bottom off of your bamboo plant, you should avoid doing so. Generally, it results in the death of the plant. However, if you have a diseased, braided bamboo plant, then you may need to remove the bottom part of the diseased stalk -- the point from which the disease will spread -- even if you cannot entirely extricate the remainder of the problem shoot. In this case, it will make sense to carefully cut the bottom off of a bamboo plant.
Pour the pure spring water into a bamboo planter. Let it sit for several hours so that it is room temperature.
Sterilize your scissors. You can douse them in rubbing alcohol to kill any potential infection, then let the alcohol evaporate before you move on.
Cut off the bottom of the problem bamboo stalk. Do not interfere with the other stalks at all. If the entire stalk is yellow or brown, then remove the whole thing. If only part appears to be diseased, you can try trimming off the diseased parts and the roots, leaving an inch of root, if possible. In most cases, this will not be an option.
Replace the bamboo in the sterile, room temperature water, which should be 2 inches deep, in most cases. Make sure all the roots are underwater.
Fertilize your bamboo plant. Add several drops of bamboo fertilizer to the water according to the manufacturer's instructions because every fertilizer product is slightly different in concentration and contents.