This study focused on developing a protocol to evaluate the viability of 256 second-hand and end-of-life rain jackets. The methodology comprised four distinct stages: visual inspection, ISO 4920:2012 Spray Testing, climate chamber rain simulation, and hydrostatic pressure testing (Suter Test). Initial visual scoring (scale 1–5) proved limited, as superficial inspection failed to detect latent structural failures. Similarly, the Spray Test was deemed insufficient for comprehensive evaluation, as its short exposure duration did not accurately reflect real-world environmental stress, limiting its utility to DWR assessment only. In contrast, the rain simulation, conducted at a flow rate of 2,700 ml/min for 30 minutes with garments mounted at a 45° angle, provided the most significant insights into garment integrity, despite its logistical complexity.