In this thesis, a diagnostic assessment of the entire water supply distribution network was carried out in order to evaluate problems associated with water supply in Calabar. This assessment was carried out by conducting inventory of all the facilities in the entire water supply distribution network by onsite, physical and visual inspection of all the elements in the distribution system during operation. Qualitative assessment of equipment/facilities physical conditions and functionality was conducted using numeric rating of 0-4. The situational analysis of the system was also carried out using performance indicators such as Service Performance Evaluation Ethics (SPEM), Sustainable Effectiveness Ranking Approach (SERA) and Strength Weakness Opportunities and Threats (SWOT) analyses. Detailed evaluation of overall operation and maintenance and pumping schedule plan was looked into. The results clearly shows that the transmission pipes, service reservoirs, pumping stations and valves in the distribution system are in good physical conditions and are functioning properly. However, most of leakages and bursts occur in asbestos pipe in the distribution system and valves in the transmission system. The system has 56% operation and 70% human resources capacity with the total evaluation capacity using SPEM as 60%. The type of maintenance carried out is simple reactive rehabilitation approach any time there is failure. A suggestion of proactive rehabilitation was made which is better than reactive rehabilitation approach. Thus, it will be appropriate to pump water from 0000 hours to 1200 hours and 12 to 18hours to meet the water demand and minimised cost of operation.