Why are sewer manholes round – a necessity or a tradition?

Why are sewer manholes round – a necessity or a tradition?
Why are sewer manholes round – a necessity or a tradition?

Why are manholes round? And what else can they be? Theoretically, the hatch can be square or rectangular. But such a design, rather, is an exception to the rule. The hatch is not a simple manhole; it must be securely closed. It should be easy to maintain and safe to operate.

If convenience is an amateur, then reliability at the level of standard loads can be ensured precisely by the round design of the cover. The configuration of the base, which, in fact, is a sewer hatch, depends on its shape.

Why are manholes round?

Sewage system

Sewer networks are a complex of facilities designed to collect and divert wastewater from users to treatment facilities. The easiest way to do this is with underground utilities. A trench is being dug, pipes are being laid in it, through which wastewater will be discharged.

To be able to service the system through a certaindistance required inspection shafts. In the conditions of urban infrastructure with dense buildings, it is possible to conduct sewer networks only along roads or directly under them. In this case, with heavy traffic, the hatches must be securely closed. But why are sewer manholes round? They must have sufficient strength to withstand the maximum possible traffic loads.

In a big city, the number of inspection hatches and various shafts can be in the hundreds of thousands. After all, this is not only sewerage, it is also a network of communications: water supply, heating networks, electricity, gas, telephony, and so on.


For ease of access to communications, the well shaft is usually made in a round shape. Sewer rings used for the construction of such structures are most often made of reinforced concrete.

The cylindrical shape of the well is most suitable for maintenance. It is more convenient to work in such mines. They are suitable for ventilation, since the air circulation in a cylindrical object is more intensive.

sewer rings

The cover size, base area and inner diameter are selected according to the purpose of the inspection shaft. In this case, all elements of the system will correspond to each other as much as possible. The location, possible loads, traffic intensity are taken into account.

Why are manholes round?

It depends on the shape of the lid. On the one hand, service personnel must haveconvenient access to underground utilities. On the other hand, the well must be securely closed to exclude the possibility of foreign objects getting inside, to ensure the safe movement of pedestrians and vehicles. A round lid is best suited for this, which means the hatch itself should be this shape.

Depending on the purpose, they are divided according to the type of communications laid under them: engineering cable networks, water supply, gas mains, heating mains, storm and sewerage. The size of the sewer manhole varies from country to country. In Russia, standard dimensions are most often used (645 and 800 mm). Hatches that are not manufactured according to GOST are designed and developed by manufacturers in accordance with the order and specific technical conditions.

Why is the manhole cover round?

Why is the manhole cover round?

This configuration has a number of advantages. Previously, hatches were made in various shapes. They could be square, rectangular, oval, and even triangular to indicate the direction of water flow. However, the round shape of the lid proved to be the most suitable.

It will never fall into the well, no matter how you twist it. A round lid is easier to open, so the point of application of force in any place of the circle will be the same. It can be rolled by placing it on edge. This design is more cost effective when manufactured.

The round shape of the lid is less prone to sagging. It withstands a large load with the same thickness, which means thatit can be made thinner without losing quality. During production, round castings give a lower percentage of rejects (shells, pores, cavities).

Manhole size


The base and manhole covers for critical sewer wells are most often made of cast iron. This material has strength to withstand heavy loads and corrosion resistance for long service life. The weight of the structures is sufficient so that passing vehicles cannot accidentally lift and move the cover. Cast iron manholes are made by remelting secondary raw materials, they are cheaper than steel counterparts.

In places where there is no heavy traffic, it is not advisable to install heavy and powerful structures. Recently, hatches made of plastic, polymers and composite material have appeared. They are lighter, cheaper, have a sufficient margin of safety, long service life.

In private houses for the arrangement of sewerage, equipment of manholes and septic tanks, sewer rings made of reinforced concrete are used. In this case, it is quite justified to install the same base for the hatch on top of them. The cover is also made of concrete. It is made of a larger diameter, does not enter the groove, but simply covers the hatch opening. The massive structure is heavy enough that it cannot be accidentally moved. This provides the necessary safety during operation.

Sewer networks

Specification and marking

For increased road loadsuse heavy hatches (class T). They may have a weight of over 100 kg and a thickness of over 100 mm. Where vehicular traffic is not provided, light hatches (class L) are used. Structures for garden, lawn and other areas (class A) have a diameter of 540 mm and a thickness of 50 mm.

Why are sewer manholes round and marked? This is done for the convenience of recognizing their belonging to utilities. There are letters on their covers: GS - gas network, MG - main gas pipeline, PG - fire hydrant, etc.

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