International developments in PVC gravity sewer design

I was privileged to present papers on the structural design of PVC sewers at the earlier Symposiums and again to report progress.

UK entry into the Common Market makes it desirable to consider further PVC sewer laying practice and the results of experience in Continental European countries. Experience has been collected and quantified ina number of different places. For instance,.as we heard at the last symposium, the KOMO authority in Holland has measured actual deformations of PVC sewers laid in various sub-soils at differing times and loading conditions. In their report KOMO made interim recommendations as to the class of pipe to be used: generally and outlined certain procedures for incorporation in codes of practice for the laying of PVC sewer pipelines. A similar, more limited measuring exercise was subsequently conducted on behalf of some of the leading PVC pipe manufacturers on widely distributed sites in the UK. The same measuring instrument, which had been specially designed for the purpose, was used for both the KOMO survey and in the UK.

At the same time in the International Standards Organisation, there is a sub-committee and four active task groups or panels investigating various aspects of the structural design of PVC sewers.
One is concerned with the drafting of a standard for PVC sewers (Finnish convenor), another is dealing with the selection of suitable formulae to predict deformation in relation to wall thickness, subsoil and loading conditions (French convenor). More recently a small committee has been set up to draft an International Code of Practice for the installation of drains and sewers (British convenor).
A fourth group has investigated and recommended the value to be used for the modulus of the PVC material after 50 years of life, i.e. the value of ‘E’ to be inserted in the Spangler type formulae.