Transmission mains are the most vulnerable parts of water supply systems. The state of the art in Austria due to condition assessment of water pipes is described in ÖVGW Guideline 105, 2010 "Failure Statistics". As given by the name of the guideline condition data generally is collected during the failure repair process. Based on this data statistical methods are used to describe future failure occurence, as a state of the art method for distribution pipes. Rehabilitation decisions are mainly based on this statistical failure prediction. This methods provide satisfying results for the supply system, but are not applicable for the transmission systems as here a failure providing strategy is necessary due to the high vulnerability of these pipes.
Direct inspections of transmission mains are not common practice so far. Mainly because of short time cost calculations and technical restrictions due to inspectability of the pipes.
The aim of this study is to investigate the possibilities and restraints of available transmission pipe inspection techniques or material tests of pipe segments, to derive practicable techniches and evaluate them due to their performance in practice (case study). Cost benefit ratios of different condition asesssment techniques on basis of life cycle cost calculations are part of the study as well. Further the study implements an integrated risk assessment (based on Friedl, et al 2011 and Möderl, et al, 2009) for an example transmission system (City of Vienna) to derive pipes with the highest risk of failure. The elaboration of an integrated failure risk asessment method has the aim to provide a decision support for condition inspection planning.