advanced drainage system - Polypipe

FAQ Section 3.8
Q. Do I need to install rocker pipes when forming chamber connections?
A. Although thermoplastic structured walled pipe systems are able to accommodate a degree of differential
settlement, we recommend that the provisions outlined in a relevant code of practice be followed.
Sewers proposed for adoption under Section 104 of the Water Industries Act, 1991.
Sewers for Adoption (6th Edition) states a flexible joint should be provided as close as possible to the outside
face of any structure into which a pipe is built. In addition, a rocker pipe be provided; to allow for
differential settlement that may occur between the structure and pipeline.
The length of rocker pipe required is generally in accordance with the following table;
Nominal Diameter Effective Length
(mm)
(m)
150 to 600 0.60
675 to 750 1.00
over 750 1.25
Table 1 Extracted from CESWI 6th Edition.
Stub and rocker pipes may be formed in the
Ridgisewer system by simply cutting pipe sections
on site to create the lengths required. Specific
rocker and stub pipes are available for the nominal
750 & 900mm pipe diameters only.
Non-Adoptable sewers
In the absence of a detailed specification, we recommend that the provisions outlined in a relevant code of practice
be followed.
In this regard we would draw your attention to BS 5955: Part 6: 1980; “Plastics Pipework (thermoplastics
materials). Part 6, Code of practice for the installation of plasticized PVC pipework for gravity drains and sewers.”
(Clause 7.3, reads as follows:)
“The provision of at least one flexible joint is recommended within 300 mm of the external face of the wall of any
building and at each entry or exit point of all manholes and inspection chambers. Where abnormal settlement is
expected, it is desirable to incorporate two flexible joints to form a ‘rocker’ length of pipe”.
Q. Do Polypipe Civils offer catchpits and chambers?
A. Polypipe Civils Limited has an extensive fabrications department that can produce chambers using either its
Ridgidrain or Ridgisewer pipe system. Catchpits and chambers are specifically fabricated to client specifications,
offering base, channel, and coupling options to enable the construction of a complete plastic drainage system.
Plastic chambers have been used for many years for the construction of manhole chambers on non-adoptable
sewers, however, it should be noted that Sewers For Adoption presently specifies that manholes to be of
brickwork or pre-cast concrete construction.
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