Abstract: The disclosed apparatus subjects samples of pipe, preferably plastic pipe, to controlled internal hydrostatic pressure in order to test the ability of that sample to withstand such pressure without catastrophic failure. A hydraulic pressure source (10) which preferably includes a variable volume compensated pump (12) and pair of accumulators (17) and (18) and applies the source pressure through a servo controlled pressure control valve (22) to a water filled sample (S). The hydrostatic pressure of the water within sample (S) generates an electrical signal proportional thereto via pressure transducer (24) and amplifier (25). This first signal is compared to an electronically generated second signal from a function generator (27). This second signal is proportional to the desired pressure within the sample (S). These first and second signals are compared by differential amplifier (28) which generates a third signal proportional to the difference between the first and second signals.