Reduction of non-revenue water is one of the major challenges facing many water utilities inrnEthiopia in general and Debre Markos water supply system in particular. So, the study focuses onrnthe assessment of water loss in water supply networks in Debre Markos town using statisticalrnanalysis, Water audit and water CAD software. A statistical analysis was applied to analyze therncurrent water supply coverage of the entire town. Water audit software was used to analyze waterrnloss components and the efficiency of the system was evaluated using different performancernindicators .Water CAD6.5 software was also used to simulation the distribution water supplyrnnetwork. Discussions were made with Local expertsâ€™ to support the quantitative analysis. From thernresult of the analysis, it was observed that the total water loss in Debre Markos water supplyrnsystem is high reaches up to 40% of the system input volume and about 33% of the totalrnsystem loss is real losses and 7% apparent losses. Besides, the average daily per capita waterrnconsumption of the town is 24 liter/person/day. In general, the low water supply coverage of therntown was highly influenced by the availability of water. However, the main reasons for the highrnloss of water in Debre Markos water supply system are the present way of water networkrnmanagement with ad-hoc maintenance and insufficient financial resources of the utility. Thus, it isrnnecessary to identify the losses encountered in the water supply system so as to take remedialrnactions in reducing the water loss more significantly.rnKey words: assessment of water loss, water supply network, water supply coverage, non-revenuernwater, water audit software, water CAD, performance indicator, Debre Markos.