For HDPE water supply pipes, the relevant BIS standard is IS 4984:2016. For unplasticised PVC pipes for potable water, it is IS 4985:2021. To sell either product with the ISI mark, the manufacturer must obtain a BIS Scheme I licence for the applicable standard and approved product scope. BIS currently lists certification for these standards as voluntary; check any buyer or tender requirement before production. In HDPE vs PVC pipe manufacturing, the licence choice follows the finished pipe, not the machine. The HDPE vs PVC pipe extrusion process and testing needs should guide your HDPE pipe machine vs PVC pipe machine comparison and HDPE vs PVC pipe plant investment. Unique Extrusion Machinery supplies lines for both materials and can help select equipment for the intended product. Conclusion: Choose IS 4984 for HDPE water supply pipe or IS 4985 for PVC potable water pipe. Apply for the relevant BIS Scheme I licence if you intend to use the ISI mark. Confirm the required pipe specification and licence scope before investing in the plant.