This experimental investigation assesses the behaviour of a solar water heater provided with a liquid heat exchanger in a horizontal storage tank. The factors that affect the stratification inside the storage tank are considered. The performance of the system is studied in the light of the daily consumption of hot water of an Egyptian family. The results obtained show that in the places where it is necessary to use a horizontal tank it must be supplied with an auxiliary electric healer to meet the required load at the required temperature, especially in winter.