Every pipe PNB manufactures carries an IS number printed along its length. That number is not decoration — it is the specification the pipe was tested against, covering wall thickness, pressure rating, material composition and dimensional tolerance. Knowing which standard applies to which product is the fastest way to check that what arrived on site is what you ordered.
IS 4985 — uPVC pressure pipes
IS 4985 governs uPVC pressure pipes for potable water supply, irrigation and general plumbing. It fixes the outside diameter and the wall thickness for each pressure class — 2.5, 4, 6, 8 and 10 kg/cm². A pipe marked IS 4985 Class 4 has a defined minimum wall thickness for its diameter, which is why two pipes of the same outside diameter can weigh differently and still both be correct.
IS 15778 — CPVC for hot and cold water
IS 15778 covers CPVC pipes and fittings for hot and cold water. The important difference from uPVC is temperature: CPVC to IS 15778 is rated to carry water at up to 93°C continuously. Sizes follow CTS (Copper Tube Size) rather than nominal bore, which is why CPVC fittings are not interchangeable with uPVC fittings even when the printed size looks similar.
IS 13592 — SWR drainage
IS 13592 is the SWR standard — soil, waste and rainwater pipes. These are non-pressure pipes, so instead of a pressure class they carry Type A (ventilation and rainwater) and Type B (soil and waste discharge) classifications. Type B has a thicker wall because it handles discharge under intermittent load.
Conduit, casing and HDPE
IS 9537 applies to rigid electrical conduit, IS 12818 to uPVC well casing pipes for borewells, and IS 4984 to HDPE pipes for water supply. Each has its own test regime — casing pipe under IS 12818, for instance, is checked for collapse pressure because it has to resist soil load rather than internal water pressure.
A one-minute check at delivery
When you receive a consignment, three checks take under a minute: read the IS number and confirm it matches the application, read the class or type and confirm it matches what was quoted, and check the ISI mark. If any of the three is missing or inconsistent, ask before the pipe goes into the ground — replacing a buried line costs many times more than rejecting a delivery.