Cylindrical type storage tanks are used in most commercial ICS systems, as they resist to the pressure of water mains. ICS systems with one or two cylindrical storage tanks combined with curved reflectors are cost effective devices and can be easily used in domestic solar applications. In this paper we compare ICS solar systems with cylindrical water storage tank and different mountings of it in a symmetric CPC or involute reflector trough. The design, construction and experimental results from four ICS systems regarding water temperature profile, mean daily efficiency and thermal losses during night are presented and discussed. The experimental models are tested outdoors under the same weather conditions and without water drainage for a sequence of 3 days, starting the first day with cold water. During tests we have recorded solar radiation, ambient temperature, water temperature in different locations inside the storage tank and also wind speed. The results show that during the day the ICS systems with a horizontal tank present a satisfactory performance in water temperature rise and heat preservation in water storage tank during night. Regarding reflector types, the ICS models with CPC reflectors achieve higher mean daily efficiency, while models with involute reflectors present high efficiency only in low operating temperatures. (C) 2003 Elsevier Ltd. All rights reserved.