The south-western coastal communities of Bangladesh face severe shortage of freshwater due to climate change, geological factors, and saline water contamination. As a result, rainwater harvesting (RWH) has become the major source of drinking water for the community. This study investigated rainwater collection techniques and the challenges associated with ensuring their adequacy for consumption. To gain a better comprehension of the process, rainwater samples were collected systematically, and household interviews were conducted to assess quality parameters, including anion and cation concentrations, bacterial contamination (total and fecal coliforms), and heavy metals (Pb, Cr, and Zn). Although the total coliform concentration ranged from 0 ppm to 120 ppm, showing no contamination of bacterial coliforms. The presence of heavy metals in all samples is within acceptable limits. Anion and Cation tests showed slightly elevated levels of nitrate (51.8640 mg/L), ammonium (1.0512 mg/L) and chloride (255.8913 mg/L) concentrations. Nevertheless, the water quality met the safety standards of consumption in accordance with WHO and Bangladesh’s drinking water standards. However, community perceptions have pointed out that inadequate storage facilities are a major limitation affecting the use of water throughout the year. The use of informal RWH systems, such as polypropylene sheets, ferrocement tanks, and plastic drums were widespread. After Cyclone Aila, metal roofing replaced asbestos cement sheets, offering durability but risking health hazards from chemical leaching into harvested water. Asbestos roofs are used for 99% of rainwater harvesting, raising health concerns. Users have emphasized the improvement of drinking water collection and storage infrastructure in Bangladesh’s coastal regions.