High density polyethylene has been widely used in marine and gas transportation, storm sewers, culverts and city drainage system. Compared with other conventional pipes, it has its own advantages, such as, chemical corrosion resistance, durability, flexibility, easy joining and subsequent easy management and fitting. In this paper, and in order to forecast the remaining lifespan of a pipe enclosing a crack and subjected to internal pressure, it is essential the assessment of K_I the stress intensity factor throughout the crack propagation. The finite element method is used to assess the values of the stress intensity factor of an axially oriented semi-elliptical crack located at the inner surface of an HDPE pipe. The crack configuration is described by the relative wall thickness (t/R), the relative crack depth (a/t) and the crack aspect ratio (a/c). The lifetimes presented are discussed in accordance to the crack size and the stress intensity factor in each case.