Code of practice for plastic pipes work for potable water supplies, Part 1: Choice of materials and general recommendations
1975 Edition

IS 7634 Part 1 (1975) advises using thermoplastic materials such as polyethylene and unplasticized PVC for potable water pipelines. It notes that tensile strength diminishes with increasing temperature, and impact strength lessens at low temperatures. To prevent deformation from prolonged stress (cold flow), cold bending stresses should be avoided, recommending the use of permanently thermoformed bends compliant with relevant Indian Standards. The standard stresses selecting materials based on their physical, chemical, and mechanical suitability for drinking water applications.

According to IS 7634 Part 1, polyethylene (including LDPE and HDPE) offers generally good chemical resistance and superior flexibility, with LDPE being highly flexible and coilable. In contrast, unplasticized PVC is chemically resistant but relatively rigid and less flexible. PE pipes are typically favored for underground and corrosive environments due to their flexibility, whereas UPVC is preferred where rigidity and higher tensile strength are required.

The standard recommends different jointing approaches based on the plastic type: LDPE pipes commonly use insert-type, compression, and threaded joints; HDPE pipes are joined by compression fittings, fusion welding, and flanged connections; unplasticized PVC pipes employ solvent welding, flanged joints, threaded or screwed joints, and rubber ring seals. These methods ensure reliable sealing and mechanical strength appropriate to the application environment.

Testing involves fully filling the system with water to expel air, sealing air vents, and visually inspecting joints and supports. Pressure is then gradually applied to at least 1.5 times the operating pressure. Due to initial pipe expansion, a stabilization period of up to 12 hours is advised, during which make-up water must be added as per specified quantities. A pressure drop not exceeding 0.2 kg/cm² over one hour indicates acceptable performance.

To guard plastic pipes against UV damage and environmental effects, manufacturers incorporate stabilizers such as carbon black. Pipes should preferably be installed underground or within protective ducts to minimize sunlight exposure. Handling precautions include avoiding rough treatment, impacts, and improper stacking. Material selection should consider permeability and local environmental conditions. In cold climates, special care is necessary to prevent damage during thawing, avoiding conventional methods.