Failures of water and wastewater networks can lead to severe consequences for the human, natural and built environments. This paper presents how data on networks and their immediate environment together with graph analysis can be used to estimate the severity of pipe failure consequences. A case study concerning a large water and wastewater utility revealed that ca. 14% of the water distribution pipes and ca. 25% of the sewers had potentially severe failure consequences with regard to at least one factor considered. The most detrimental failure modes connected to these pipes were identified. An assessment of the most important information needs revealed that a number of crucial source data sets were missing. The results can be used to support asset management decisions aiming at risk alleviation, e.g. when estimating the resources needed for network maintenance, condition inspections or renovations and when planning excavation works.