A recent backpacker returned from Kilimanjaro with water samples to test how well it was being filtered and treated on the mountain. In this case, the answer is not well at all! As a result a number of climbers became ill. While I’m only aware of a few cases where climbers got sick on the mountain (aside from altitude sickness), water quality is a serious issue on Kilimanjaro. On one climb I witnessed a porter urinating into the steam that was to be our water supply.
There are a few things you can do to protect yourself on the mountain. If you bring your own filter make sure you get your water far enough upstream to avoid any contamination from your own party. If the porters are providing all your water make sure to ask your guide how the water is being purified. Warn him that you’ve heard stories and do not want to get sick. The guides know sick clients mean lower tips and should take extra precautions with your water.