Testing of pipelines

Visual inspection (pipelines larger than DN 600) 6.11.1

The contractor must carry out an internal visual inspection of pipelines larger than DN 600 nominal size after compaction of the backfill. All defects in jointing and obvious points of infiltration must be noted and repaired to the satisfaction of the Superintendent.

Ovality testing 6.11.2

Ovality is a pipe cross section which is out of round and measured as a percentage variation in pipe diameter. The maximum permitted ovality is 3%.

The contractor must test all HDPE profile-wall pipelines for ovality:

  • For pipelines less than DN 600 the contractor must determine any excessive ovality using a proving tool to a design approved by us, set to determine ovality exceeding 3% of the internal pipe diameter when round. The proving tool must be supplied by the contractor. Ovality testing must be undertaken at least 14 days after compaction of backfill. The contractor must replace lengths of pipeline having excessive ovality.

  • For pipelines larger than DN 600, the contractor must determine any excessive ovality by measuring the internal vertical and horizontal diameters at the mid-length and at the joints of the pipeline. Measurements must be taken after laying and jointing of the pipe on the minimum depth of support material.

24 to 48 hours after placement of the backfill. All measurements must be taken at the same location between indelibly marked points on the pipeline. The instrument used to measure the pipe diameter must be accurate to within one millimetre.

Pipes having excessive ovality must be re-laid by the contractor at the contractor's expense.

Rectification of faults 6.11.3

When inspected or tested in accordance with Testing of Pipelines, if any section of drain fails to attain the standards required by this Specification, the fault must be located and rectified by, and at the expense of, the contractor.

Defective or damaged pipes and fittings must be removed and replaced. The relevant tests or inspections must be repeated until the required standard is attained.

Cleanliness and flushing 6.11.4

After backfilling and before the pipelines are tested, the contractor must flush the pipes with clean water to remove all clay and other material. No line will be accepted which doesn't present a clear barrel free from sand, clay or other material, lips or other obstructions. Such lines must be kept clean until handed over for use by us.


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