The objectives of this paper are to study the contribution of iron uptake and hydraulic entrainment to the generation of red water in a pilot scale distribution system and to establish the factors affecting iron uptake. Most of the research was done on a pilot scale distribution system which represented a simplified version of the field situation. The main modification made to the system was the incorporation of two experimental pipelines which were composed of unlined cast iron test sections and were designed to model the effect of two different flow regimes experienced at the distal parts of distribution systems. Aesthetic water quality was monitored by spot sampling for iron, turbidity, color, and UV. Continuous water quality monitoring was also carried out for the following parameters: pH, temperature, dissolved oxygen, turbidity, conductivity and redox, using a multi-parameter monitor which recorded data every minute. Red water experiments were run from May 1997 to March 1998 and were designed to improve knowledge of red water in the first year of installing unlined iron mains. Throughout the experiments turbidity was used as the main surrogate measure for identifying aesthetic deterioration due to the presence of iron.