Abstract This study investigated the quality of drinking water supplied to the general drinking water network of Tripoli city-Libya (tap water and ground water). A total of four different sites were selected for this study. The chemical and biological parameters were carefully determined and compared to the WHO and the Libyan standard. The chemical analysis was performed mainly to estimate the level of some heavy metals (Zn, Cd, Cu, Pb, Fe) using atomic absorption spectrometry followed by biological test using the Most Probable Number (MPN) method for a possible microbial contamination. The obtained results of both chemical and biological analysis revealed that the distributed water is safe to drink except in one site. The analysis also showed that the quality of water remains mostly unchanged in terms of chemical and biological (micro-organisms) aspects. Estimation of heavy metals was below the limits. The % RSD value was less than 2.5 % based on triplicate run. Overall, investigation of both chemical and microbial aspects is an effective method of monitoring quality of drinking water. Such investigation is needed to identify possible sources of contamination which could be storage tanks and pipeline to ensure the reach of safe drinking water to the users.