There are many reasons that manhole covers are round in shape. Each of them is described below.
- If covers are square or rectangular, then there are chances to accumulate fungi or algae or other sewage material at corners. Since circular pipes have no edges this could avoid the problem
- Round covers are easier to manufacture than other ones
- The placing of cover on manhole is easy as against of rectangular. Say, a rectangular cover has a chance to fall into the sewage pipeline.
- Circular manhole covers are easy to place and manufacture in bulk.