The potable use of harvested rainwater is limited, mainly due to contamination with various pathogenic microorganisms. Disinfection of microorganisms by solar photocatalysis is emerging as a promising technique for drinking water treatment. The present study deals with the preparation of Ag-doped TiO2 by the sol gel method, and its immobilization over the inner surface of the Pyrex glass pipes used in fabrication of pilot-scale reactors. The solar photocatalytic efficiency of the reactors was tested for the disinfection of microorganisms in tap water and roof harvested rainwater. The photocatalytic experiments under solar irradiation illustrate that doping with silver ions significantly increases the inactivation rate of all microorganisms compared with pure TiO2 and direct photolysis. The inactivation efficiency against various microorganisms was found in the following decreasing order: E. coli>MS-2 phage>Aspergillus spores. The roof harvested rainwater was completely disinfected in addition to chemical oxygen demand (COD) removal, within 120 minutes of solar irradiation. The experimental cycle was repeated several times to study the stability of the reactor. The pilot-scale solar photocatalytic fixed bed tubular reactors were found to be very effective for the disinfection of rainwater for potable use.