| Corrosion and deterioration state of service pipes were evaluated by using indirect diagnostic methods such as facility information, short-term historical accident records, questionnaire, water quality, water pressure, and leak detection according to the periods of water supply in major three water basins. Results of facility information and short-term historical accident records showed that the accident ratio of GSP(Galvanized Steel Pipe) was higher than other service pipes, and mostly service pipes of buildings that the periods of water supply were over 10 years were renovated with A/S & Epoxy lining technique or replaced with new anti-corrosive pipes such as stainless steel pipes or synthetic resin pipes because of the increase on residential affairs such as generation of red water, leak, and deterioration of water pressure. The results of questionnaire on residents also showed that the degree of unsatisfaction for water quality, water pressure, and leaks tended to be more increased as the periods of water supply was more increased. The results of analysis on water quality collected from buildings showed that there were not prominent characteristics according to the periods of water supply, but all buildings were not satisfied with Standard of Drinking Water on residual chlorine(0.2㎎/l). The results of measurements on water pressure at a tap showed that the trends on the decrease(the way of water tank) or the increase(the way of direct connection) of water pressure according to the periods of water supply were not distinctive. But ratio of households that drinking water was supplied under standard water pressure according to the periods of water supply were increased because of the decrease of their hydraulic cross sectional areas. Lastly, the results of leak detection showed that leak generation rate of buildings in HRB was higher than other basins. And buildings that the periods of water supply were in the range of 11 to 15 years had more higher leak generation rate than other periods of water supply. Especially GSPs mostly have been rehabilitated before and after ten years of water supply. At that time Average and Maximum Erosion percent were in the range of 6 to 8% and in the range of 10 to 15% respectively. But More researches are required to decide the time on rehabilitation correctly because of many various factors that affect corrosion and deterioration of service pipes. And Average and Maximum Erosion Percents of NRB were higher that other basins, so if the periods of water supply were the same, service pipes of NRB were more quickly deteriorated than other basins. |
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