This paper describes two new measurement techniques that are in use in the United Kingdom to help make informed decisions about the need for maintenance of water mains to improve conveyed water quality to customers. The first technique involves the use of a new instrument, the "Trunk Mains Sampler", which has been designed to sample deposits from inside trunk mains, under pressure, without interruptions to supply or causing discolored water problems to customers. The purpose of the sampler is to provide objective measurements of deposits, from which it is possible, together with additional information such as conveyed water quality, to ascertain priorities for trunk mains rehabilitation, typically for mains greater than 6". A camera, which can also be inserted into trunk mains under pressure, has been developed and used to provide visual confirmation of the presence of sediment and the condition of the trunk mains. A description of the development work, the operation of the sampler and the interpretation of the results is given. Case studies of recent applications of the sampler to determine mains rehabilitation requirements are also provided. The paper also describes a sampling method and results from a project aimed at establishing the factors affecting the build-up of sediment in small diameter distribution mains. The objective of the project was to establish ground rules and trends to predict the risk of deposit build-up within distribution systems to help target maintenance flushing of small diameter mains, and swabbing of larger diameter mains. Includes tables, figures, appendix.
