The polyolefins constitute a significant amount of domestic waste: 40% of all polymeric products based on polyolefins have a short-time service life and 38% of these products are disposed in landfills. Since the plastic wastes may be obtained from several sources, they might had been exposed to different storage and processing conditions and may exhibit different behavior depending on the degradation level. The impurity removal is critical and has significant effect in durability of the final product. In that context, the incorporation of waste in materials for structural application demands a series of technical evaluation procedures that need to be assessed, especially when the materials undergo constant pressure. This work aims to characterize the main impurity materials that are commonly found in recycled High Density Polyethylene (HDPE) and to evaluate the effect of its content in both short-term mechanical behavior and stress cracking, comparing these properties to the ones of pristine HDPE. The study was carried out by means of tensile and impact tests, melt flow index (MFI), and Un-notched Constant Ligament Stress Crack Test (UCLS).