Pigging in the maintenance of pipelines refers to the practice of using pipeline inspection gauges or ‘pigs’ to perform various operations on a pipeline without stopping the flow of the pipeline.

The cleanliness, bore, linearity and joints inside the small diameter, say 450mm or less, drainage pipelines will be tested by pulling a mandrel through the completed pipeline after completion of work. The mandrel is about 750mm long and 12mm less in diameter than the nominal diameter of the pipeline being tested. If specified under the Contract, this internal inspection may have to be performed by closed circuit television ( CCTV ).