一城市居民院内经常有大量排泄污、雨水的下水管道堵塞,每年为此要疏通、维修。仅北京平房院内的下水道就有三百万平米左右,目前最少每年平均疏通一次,按现行的劳动定额计算、需要二十一万个工日,即七百名房屋维修工人长年干这项工作。为什么下水 There is often a large number of sewers that drain sewage and rainwater in a city resident’s hospital. It is necessary to dredge and maintain it every year. The sewerage in the Beijing Bungalows alone is about 3 million square meters. At present, it is dredged at least once a year. According to the current labor quota, it needs 210,000 work days, that is, 700 house maintenance workers do this work for many years. . Why is it in the water