The development of unwanted deposits in any water distribution system is unavoidable under standard conditions. Knowing the composition of such deposits will help to establish the causes of deposit formation and consequently to be able to keep water quality as high as possible. This paper presents the results of an extensive study of deposits found in a water distribution system of a tropical city. Characterization of materials collected across the system was made by infrared spectroscopy (IR), X ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). Analysis of the samples taken at several sites of the system reveals the presence of three predominant deposits: a brown coloured deposit, tubercles and white deposits. Aluminosilicates and humic acids were found to be main constituents in brown deposits. Tubercles were mostly mixtures of magnetite, goethite and in some cases lepidocrocite. White deposits were formed by calcite, aluminosilicates and quartz. Organic matter as volatile solids were 14.0 ± 5.0% for brown deposits and 11.2 ± 2.0% for tubercles.