(i) Each pipe shall be tested by the manufacturer and shall withstand a hydraulic pressure to one and half times the design pressure but not greater than pressure calculated by the following formula given below.  In the absence of working pressure is indicated in the Test Certificate then the tested pressure indicated in the Test Certificate divided by 1.5 shall be the maximum working pressure 

P = 2 S t / d                          

where     P = test pressure

                D = specified outside diameter of the pipe

                t = specified wall thickness of the pipe

S = stress which shall be taken as 40% of the minimum tensile strength at room temperature.

(ii)  Notwithstanding anything contained in the above clause, the hydraulic test at the maker's works may be dispensed with provided that the pipes are subject to non destructive testing by an appropriate method like Ultrasonic or Eddy current or stray flux testing