BPI pipes due to their material properties expand when subject to pressure, which influences the test result, this may also be affected by differences in temperature of pipe and test medium resulting from a high thermal expansion coefficient of the pipe material, a change of 0.5 to 1 bar. Thus, the test medium should be kept at constant temperature throughout the test acc to DIN 1988 TRWI the pressure test must be performed 1.5 times of the operating pressure. Using cold water, the pipe system should be filled slowly and bled completely using calibrated measuring instruments that indicate pressure changes of 0.1 bar wherever possible. Measurements should be taken at the lowest point of the pipe system.
Where pipes and fittings have been welded, the pressure test should not be performed before two hours have elapsed after the last welding operation. The pressure test consists of two stages: For the first stage, a test pressure equal to the permissible working pressure plus 5 bar should be applied twice within 30 minutes at 10 minute intervals. Then the pressure should be checked. In case more than a 0.6 bar drop occurs over a period of 30 minutes at a rate of 0.1 bar/min, then a leakage is reported. The second stage should follow the first stage without interval and should last minimum of 2 hours. Then the Pressure drop should be checked. If the pressure drop is more than 0.2 bar and the pipe work shows signs of leakage, then the network should be corrected and the test must be repeated.