4.3.1 Water draw method

The calibration of a pipe prover by the water draw method requires standard capacity measures (volumetric method) or a weighing instrument with a tank (gravimetric method) to determine the base volume of the prover. To allow a continuous and uniform flowrate to be produced, the base volume of the prover may be transferred into a holding tank using arrangements such as those shown in Figures A.7 and A.8 . This volume is then measured either gravimetrically or volumetrically by transferring the liquid into standard capacity measures. The prover shall be thoroughly flushed and cleaned before calibration.