Abstract
The ageing of the water distribution systems has recently become a significant issue in Japan. Majority of the water pipelines are buried underground and cannot be visually inspected, which increases the difficulty of pipeline maintenance. The poor pipeline conditions only become apparent after the occurrence of a water quality incident or leakage. Therefore, in-pipe endoscope cameras have attracted considerable attention because they are one of the few non-excavation methods that can be used to diagnose the condition of a buried pipeline directly without cutting off the water supply
In this study, we analysed the data obtained from the in-pipe camera inspections conducted over the past 15 years, including samples of both the ductile iron pipes and the cast iron pipes. We verified the images of the pipe interiors from the in-pipe camera inspections and assigned scores of S through D to each pipeline with respect to the following five categories: rust status; adhesion of substances to the inner surface; status of the inner coating; sediment and suspended matter. We further classified the pipelines with scores of S and A as ‘Good’ group and those with scores of C and D as ‘Bad’ group.
We conducted factor analysis using Hayashi’s second method of quantification to clarify the relations among the deterioration in the pipe, the evaluation scores, the basic information about the pipeline and the water quality data. Our analysis revealed a very high rate of accurate classification (82.1%). Based on the category score, the status of the inner coating was observed to have the most influence on the deterioration of the pipe; we also confirmed that the water quality factors, such as the manganese concentration in raw water and the pH as well as the hardness of the purified water, affected the pipe deterioration.
