Inspection manhole products are precast concrete and reinforced concrete access structures used to allow inspection, maintenance and cleaning work to be carried out on sewer and storm water lines. Because the moulds, concrete, dimensional accuracy and curing process are controlled under factory conditions, production quality and the installation arrangement are more predictable than with in-situ construction.
Precast inspection manholes consist of a vertical access shaft, positioned at set intervals along the line and connected to the pipelines through the base unit, and top units for the cover. The system is completed by the base, the shaft units and the top units selected according to the project, working together.
Inspection manholes are generally larger than property connection chambers and are used for access, inspection and maintenance on main and branch lines. In this respect, they differ from property connection chambers, which serve building connections, and from storm water gully systems, whose function is to collect surface water.
Typical Areas of Use
- Main and branch sewer lines
- Storm water collector lines
- Inspection and maintenance points on the line
- Infrastructure access structures in industrial and residential areas
Key Advantages
- Controlled production: Provides dimensional consistency and repeatable quality at the joint surfaces.
- Fast installation: Eliminates the need for moulds and casting on site.
- Compatibility with pipelines: Base units are detailed to suit the diameter and direction data of the line.
- Structural strength: Designed taking into account soil, traffic and environmental loads.
- Ease of maintenance: The access space and internal surface layout make inspection and cleaning work easier.
Structural Components
Inspection Manhole Top Units (Cone, Taper and Frame Assembly)
These are the transition units that connect the shaft units to the cover level. In the taper (Ankara cone) unit the narrowing is concentric, whereas in the cone unit it is eccentric. The choice between the two types is made according to the layout of the manhole and the surface works. The frame assembly is the top unit that sits on the cone unit or on the Ø625 manhole opening. In the standard installation arrangement of this product, the cover sits directly on the frame; level matching is assessed according to the product's installation detail.
Inspection Manhole Shaft
This is the vertical shaft unit that sits on the base. One or more shaft units can be stacked to reach the required manhole depth. The shaft is designed to transfer vertical loads and superstructure effects to the base and the ground, while forming the access space for maintenance and inspection.
Inspection Manhole Base
This is the lowest unit of the manhole system. The pipe inlet and outlet openings, the flow-guiding channel and the connection surfaces are located on this unit. The pipes on the line are connected to the base, and the flow is directed in a controlled manner by the geometry formed in the base.
Integrated-Gasket System
In integrated-gasket inspection manhole products, the gasket is supplied as part of the joint detail of the selected unit. When the manhole units or pipe connections are joined, it contributes to watertightness at the joints. The aim is to limit wastewater leaking out and groundwater entering the manhole. The joints at which a gasket is provided vary according to the product type; installation is carried out in accordance with the detail of the relevant product.
Main Advantages
- Watertightness: Helps to limit the passage of water at the gasketed joints of the manhole system.
- Ease of installation: Supplying the gasket with the product makes it easier to complete the joints properly on site.
- Joint compatibility: Supports system integrity with compatible units and within the movement limits permitted by the product.