We bought a few ceramic filter candles from local stores on our last trip to Kathmandu (June 2017), these are the most common filters used by Nepalese. We tested their capability and compared the results with the filters we bought in the USA.
Water samples were taken from Lake Elizabeth, Fremont, California and the FirstAlert Drinking Water Test Kit was used. Three tests were conducted on 1) unfiltered water 2) water filtered by a Kathmandu candle and 3) water filtered by a USA dome.
We found that in general, the Kathmandu candles perform on par compared to the USA domes. They both were able to filter out bacteria and a small amount of nitrate. The Kathmandu candles also added some chlorine to the water. The USA domes last twice as long as the Kathmandu ones (6 vs. 3 months), but is much more expensive ($12 vs. $1.50).