Experiments were carried out to evaluate the performance of various types of drip irrigation emitters, widely used in Israel, using waste water from a storage reservoir. Fine particulate matter agglomerated by microbial by-products and in-line developed biomass were the principal clogging agents. Clogging fluctuated, increased as water quality deteriorated and decreased when it improved. There were definable differences between emitters of various types as to their clogging susceptibility which were not directly correlated with differences in emitter flow-rate, although, for any particular type, the emitter with smaller discharge was always more sensitive to clogging. The clogging process generally started with emitters located at the far end of the lateral and partial emitter clogging was more common than complete plugging. Overflow was also found in most emitter types and was more common in regulated emitters. Reliable long term operation of most emitter types was achieved with filtration at 80 mesh (180 μm opening) combined with daily chlorination and bimonthly lateral flushing. Regular lateral discharge monitoring was found to be a convenient way to detect the initiation of the clogging process. Chlorination was most efficient when applied before the emitters became massively clogged.