Whether we are talking about a sewage inspection manhole or a siphon manhole for white water, the plastic manhole can be constructed in two different ways:

Moulded polyethylene manholes consist of a circular PEMD moulded base section, obtained via a rotomoulding process. This group also includes moulded tee fittings, which are also used as manholes as well as connecting elements between pipes.

The moulded manhole is assembled directly by the company on site together with the other components (riser and conical adapter). The moulded base is prepared at the factory by drilling the base and welding the corresponding half-sleeve for the corrugated pipe or smooth pipe socket as per customer request. The connection between the moulded base and pipe is the same as the connection between pipe and pipe to ensure a perfect watertightness of the entire sewer system.

The moulded base manhole is assembled as follows:

  • connection between inlet/outlet pipe and moulded base: the pipe must be pushed until it reaches the inner ledge of the manhole;
  • installation of the strip-shaped seal on the truncated cone of the moulded base;
  • installation of the coupling extension on the base until it rests completely on it;
  • insertion of the seal into the internal space between the last two ribs of the coupling extension;
  • installation of the conical adapter until it is flush.

Manholes obtained from pipes are composed of corrugated polyethylene pipes suitably cut and welded. The manhole may have a plain bottom in the case of a through pipe or it may have a flat bottom. In the first case, fins made of polyethylene plates inclined by 8° to the horizontal line are inserted into the manhole. The manhole bottom is composed of a polyethylene plate which is welded on its internal wall with a different thickness depending on the depth of laying. On request, it is also possible to make bottomless plastic manholes that can be used to disperse water into the ground.

A ladder with polyethylene uprights and polyethylene steel-covered posts can be welded on the internal wall of the manhole.

Moulded manholes                            Pipe manholes