This paper describes the conceptual design of the water supply system for the western area of the City of Rabac, using the WaterCAD V8i program owned by Bentley Systems. The observed part of the City of Rabac covers forty households, three hotels, one camp and one industrial facility. Entire system is designed to meet requirements for supplying mentioned consumers with drinking water and for protection in the case of fire breaking out. In order tu ensure minimal costs, system provides gravitational flow of water. Volume of water reservoir was calculated as a sum of operational storage, fire suppression storage and standby storage. Its value is 850 m3. Pipeline route si placed vertically on the isohypses and along the roads in Rabac. Chosen pipeline material is high – density polyethylene. The main supply pipeline is devided into 3 segments. Segment 1 supplies tourist objects, while segments 2 and 3 supply the population and industrial facility. In the WaterCAD V8i program are made charts that show oscillations of water masses in the water reservoir, water flow charts and velocity charts. A comparison of two scenarios was made, where the first includes a condition without the occurance of the fire and second a condition with the occurance of the fire in the City of Rabac and in the industrial facility, in the period form 12 to 14 hours. Also, a comparisson of the influence of different materials (PEHD, steel, ductile iron) on water velocity and working pressures was made.