In addition to slotted pipes, an important ally for the drainage and dispersion of rainwater into the ground is the absorbing manhole.

The absorbing manhole is nothing more than a vertically buried, slotted pipe; installation should not be too deep, so a pipe with a stiffness class of SN 4 kN/m2 will suffice.

The absorbing manhole, in order to perform its task, must have slots along its entire circumference.

The manhole can have a bottom or not, this depends on the expected amount of rainwater and the desired rate of dispersion. Rainwater storage manholes generally have a bottom that allows fluids to slowly flow into the ground through slots on the circumference. In bottomless absorbing manholes, the water tends to pour into the ground immediately, much of it will disperse vertically but much will seep through the side slots.

Rainwater manholes are therefore composed of:

  • Conical reducer to fit on the riser. This tapers the riser to the size of a crawl space;
  • Fitting inserted by a gasket on the outer wall of the riser to allow PVC or polyethylene pipes, which are also slotted, to be inserted;
  • 360-degree slotted riser forming the body of the absorbing manhole;
  • Closure plate that is welded to the inner wall of the riser.

Since it is a pipe, the final height of the manhole can be reduced on site with the appropriate tools to change the length of the riser as desired.

Drainage manholes combined with drainage trenches form a complete system for draining and dispersing rainwater into the ground.

Absorbing Manholes                           Our Dispersing cells