The inclusion of manholes enables the pipe runs to be rodded through in case of blockage and tested in case of suspected leakage. Gentle bends are only permissible in those sewers large enough to be actually entered.

• 设置人孔/检查井可以使管道在堵塞时便于疏通,在怀疑有裂缝时便于检查。在进人的管道中,其弯度必须是平缓的。