"Whole of life" cost benefit
Initial Cost of Supply
In large sewerage schemes all types of pipe are considered by Authorities not only on initial cost of supply but also on the performance of the pipe to provide the most benefits to the Asset Owner.
In subdivisional developments the Developer is mostly concerned with initial costs and it has been on this basis that tender documents have been structured to the extent that in some cases only one pipe material is specified.
Generally clay pipe supply costs are higher than uPVC pipe. Thus it is only when Whole of Life Cost Analysis principles are used, that clay pipe becomes the preferred material.
Construction Costs
Specifications for construction of a sewerage line generally favour rigid clay pipes over flexible uPVC pipes because of the inherent strength of clay pipe. Because of this inherent strength in a clay pipe, the Contractor has the advantage of using Type 1 as the minimum bedding and support requirement specified by Sydney Water with the comfort that the pipe will not deform from construction or backfill settlement loads.
The flexibility of uPVC necessitates the use of Type 3 as the minimum bedding and support requirement specified by Sydney Water to assist the pipe withstand the applied loads without deformation.The extra costs in construction of a uPVC line for the material and care in placement of the Type 3 support must be taken into account by the Contractor in the preparation of his tender. Unfortunately this is not always the case as the Contractor attempts to meet market prices.
Contractors are obliged to carry out ovality testing on uPVC sewerage pipelines before acceptance and handing over to the Asset Owner. For this ovality testing to be meaningful, the testing should be delayed until all construction and settlement loads have occurred. As deformation is a critical factor in the long term (and short term) performance of uPVC pipes, ovality testing at the end of the maintenance period should be enforced by Asset Owners.
The cost of this testing and the costs determined by risk analysis should again be taken into account by the Contractor.
Notwithstanding the high interface rubber ring pressures design to inhibit root intrusion, the full range of SuperSleve Pipes can be joined easily by the traditional manual crow bar and block method.