When a sewer connects with another sewer at a significantly lower level, a manhole may be built on the lower sewer incorporating a vertical or nearly vertical drop pipes from the higher sewer to the lower one. This pipe may be outside the chamber and encased in concrete, or supported inside the chamber, which should be proved to the higher sewer and to the vertical drop pipe for inspection and maintenance. If the drop pipe is outside, a continuation of the sewer should be built through the chamber wall and the vertical drop pipe continued up to an access cover at ground level, and encased in concrete. If the drop pipe is inside, it should have adequate and accessible means for rodding. The diameter of the backdrop should be more than sufficient to discharge the maximum flow from the incoming pipe.

由于是学文科的，这种东西是在翻译不好，那位好心人能帮忙翻译一下，我这星期要交稿子的，先行谢过大家了