Why are manhole covers round and not rectangular?

It was about 350 a.d. When the Romans created the first underground sewage system, it consisted of intricate aqueducts that drained local swamps and carried waste to areas outside the walls.

Roman sewers, which were dug by hand and lined with bricks, had access roads so that the civil engineers could carry out proper maintenance. A heavy stone slab was placed over those doorways, as a sealing system; This stone panel would be a predecessor to the “manhole cover”.

It was not until the 19th century that manholes and manhole covers were developed using more advanced materials and installation techniques, but starting with Romanesque foundation and design.

The cover must satisfy a series of characteristics: on the one hand, it must be strong to withstand the passage of vehicles and people, but at the same time it must be easy to remove to allow access for maintenance teams.

The material with which the covers are made is mainly determined by the location and the type of traffic to which it will be subjected, in this way there are galvanized steel, stainless steel, aluminum, concrete … Recently the frequent thefts, for later sale as scrap, have made it necessary to use different materials , such as propylene or composite.

The key is its fixed diameter

The geometry used in its design is no accident, as the circular cover makes it possible to roll it from one place to another for transportation, moreover, it can be held in place from any angle.

In addition, being circular they have a fixed diameter and this physically prevents the caps from falling through the hole, because the distance between the center and any point is always the same, which is not the case with other geometries. If it’s a square, for example, it can shift and fall into the sewers.

When parallel-shaped covers are used, it is because they are designed to protect manholes, electrical distribution networks, or other types of wires, such as telecommunications.

The most popular manhole cover in the world

Rome is perhaps the most famous sewer in the world: Boca della Verita, whose image has lingered in the retinas of all of us after appearing in Roman Holidays, with Gregory Peck and Audrey Hepburn.

La Bocca della Veritá is one of the most photographed corners of Rome, but perhaps what many tourists don’t know is that there is an activity known as Drainspotting which consists of photographing manhole covers anywhere in the world.

Thanks to these photography artists, we have been able to get acquainted with the huge collection of designs with manhole covers in Japan, where it becomes real street art.

The Japanese government gives manhole covers manufacturers complete freedom with one caveat, they are required to include a code related to the region or region. Thus, for example, in Kyoto it is a turtle, a symbol of wisdom and longevity.