The history of the manhole cover goes back thousands of years. Even the old Romans used stone covers for their sewers. The classic round design has been established since the 1870s and since then not much has changed in the appearance of the typical manhole cover.
And why are manhole covers mostly round?
As in many cases, the dimensions of manhole covers are also classified and standardised according to DIN standards. The diameter of a round trunking cover is 61.5 cm. There are two decisive reasons for a round cover:
- Trunking workers can roll a round manhole cover and thus easily transport it.
- A round cover can never fall into the shaft because it is always larger than the shaft. It can also be easily adjusted privately with the lid of a saucepan.
The most important reason for a round manhole cover is therefore to reduce the risk of injury to the man working in the manhole. It’s hard to imagine the damage that an average 50 kg trunking cover would cause to people and technology in the shaft.
What happens to a manhole cover in heavy rain?
You can read about the power of water in the article “Torrential rain of the century – what does this mean?“. The blog post describes the effects of heavy rainfall events on the public sewer network.