Today it is recognized that SCG is the most expected origin of failure in transport systems using HDPE pipes. According to the PPI, the PENT (Pennsylvania Notch Test - ASTM D 1473) is a laboratory test performed to measure the slow crack propagation resistance SCG. In the present study, a probabilistic approach based on the PENT test is adopted to study the reliability of a polyethylene pipe. The estimated lifetime is calculated on a reliability-model. Several parameters are used to establish parametric analysis such as crack length, pressure and service temperature. The aim is mainly to use probabilistic tools to estimate the HDPE pipe lifespan reliably i.e. operating safely service. β the reliability index is calculated based on the crack size. PENT test was considered, the values obtained from β are limited (the majority not accepted) according to the length of the crack. We note that for values of 100 µm β value close to 3.7272 recommended by manufacturers.