Measuring use of household drinking water filters: field experiences from Ethiopia

In rural Ethiopia, household defluoridation filters have been distributed in an effort to reduce fluoride exposure through drinking and cooking water. Submersible dataloggers were used to measure stored water levels in household filters, and to calculate the frequency of filter filling, as well as the amount of water added to and withdrawn from filters. These quantitative estimates of filter use are compared against different measures of self-reported filter use. Tally counters were also investigated as an alternative to simple self-reported filter usage. Comparison to datalogger records shows that tally counters underreport the frequency of filter filling, while household reports of filling frequency matched rather closely. However, households report treating much larger volumes of water than were calculated from datalogger records. Datalogger records indicate consumption of approximately 12.5 litres per day per filter, or 2.0 litres per person per day, which is probably adequate for drinking but not for cooking.