Sections of pipe, 500 mm long and 100 mm in diameter, have been exposed in an experimental 1.3 km-long, one-pass drinking water distribution system since 1994. The pipe sections were obtained from manufacturers that supply pipes to the water industry and consisted of cement lined, bitumen lined, MDPE (medium density polyethylene), epoxy re-lined and exposed iron. Glass sections of the same length and diameter were studied as an inert control material. Three pipe sections of each pipe material were removed in 1995, 1996 and 1997 and the deposits scraped from the pipe wall surface. Quantitative and qualitative analyses were then carried out on the samples including infrared, elemental analysis and electron microscopy. Microbiological parameters were measured using standard plate counts. Scanning electron microscopy was used for visual and elemental analysis. Results are discussed in relation to materials used in distribution systems.