Reliability analysis of the vacuum sewerage system with use of the total probability theorem

The field reliability test conducted in the real operation conditions is the basic of water networks unreliability assessment. This kind of tests has being conducted in Poland more than 35 years. The newest results of the tests for water networks in the biggest cities in Poland have been presented in the report. Data concerning failures of the pipelines have been gathering in the Geographical Information Systems in these cities. The unit intensity of failures (failures/km year) was used for pipeline unreliability/reliability assessment. This kind of index is very useful for assessment and reliability/unreliability different pipeline comparison. Analysis of the intensity of failures values from the last 10 years operation period of networks showed that Polish networks unreliability decreased close to 3 times. Although the progress intensity of failures of Polish networks is much higher than intensity of failures of networks in many European countries. The influence of the main factors i.e. instability of ground, value and changing of the water pressure in network, pipeline material on failure frequency of the water network was also presented in the paper.