The meaning of Schedule in the world of piping systems is a reference to how heavy or light duty the piping component is. Pipe Schedule details the thickness of the pipe or more specifically the wall thickness of pipe with respect to different internal pipe bore diameter. Under this system the pipe diameter remains same for a particular nominal diameter designation. For eg a 2” pipe will have the same outer diameter for Sch 20 or sch 40 or sch 80 or sch 120 systems however the thickness will keep increasing in the same order.
The system is prevalent in Iron pipes and hence this is also called the Iron pipe size (IPS) system. In order to maintain parity, plastic pipes have also been developed on the similar concept.
In India UPVC pipes for cold water plumbing applications is based on the IPS system and both Schedule 40 and Schedule 80 pipes are being used for plumbing applications for cold water supply for residential, commercial and industrial applications.
Schedule 40 (Sch 40) PVC pipes are available in: ½” (15mm), ¾”(20mm), 1” (25mm), 1 ¼”(32mm), 1 ½”(40mm), 2” (50mm), 2 ½”(75mm), 3” (90mm), 4” (110mm), 6” (160mm) & 8” (200mm)
Schedule 80 (Sch 80) PVC pipes are available in: ½” (15mm), ¾”(20mm), 1” (25mm), 1 ¼”(32mm), 1 ½”(40mm), 2” (50mm), 2 ½”(75mm), 3” (90mm), 4” (110mm), 6” (160mm) & 8” (200mm)
Schedule 40 PVC Pipe is a lower wall thickness pipe that withstands good pressure at temperatures upto 60 Degree C. These PVC pipes are widely used for cold water supply in residential and commercial buildings and individual homes. The piping system is also used for water supply mains for large residential developments.
Schedule 80 PVC Pipe is a higher wall thickness system that withstands high pressure at temperatures upto 60 Degree C. These PVC Pipes are used for cold water supply in high rise residential and commercial buildings and applications requiring high pressure water. Due to this reason, these pipes are used for many industrial applications.
The first spotted difference between these two pipes is their design. Schedule 80 PVC pipe is designed with a thicker wall when compared to schedule 40 PVC pipe. Pipes with thicker walls have great structural & chemical durability, and resilience to strain and pressure. For these reasons, schedule 80 pipe can handle higher pressures because they are thicker and stronger.
Schedule 40 pipes are most commonly used for drainage in residential and commercial buildings and can be easily found in any hardware store. Best suited for cold-water systems, schedule 40 pipes are strong, rigid, and can handle pressure applications.
However, for applications that require higher pressurization, schedule 80 pipes are best suited. The amount of pressure is terms as pounds per square inch or PSI. a 4″ schedule 80 PVC pipe is rated at 320 PSI while a 4″ schedule 40 PVC pipe is only rated at 220 PSI. For these reasons, schedule 80 pipes are most often used in heavy-duty commercial and industrial applications.
NPS or the Nominal Pipe Size measurements of both schedule 40 pipe and schedule 80 pipes are the same for the same pipe sizes. Even the Outer Diameter (OD) of the pipes will remain the same for both the scheduled pipes; however, the difference is between the Inner Diameter (ID). Additional material is used in schedule 80 pipes to increased the thickness of the sidewall on the inside of the plumbing only. The advantage here is that the pipes can use the same fittings for both the piping. Another advantage is that pipes can be threaded to same standard as the iron pipes and thus become compatible to the common Indian thread system of IS554.
Schedule 80 rated plumbing supplies have a higher purchase cost when compared to schedule 40 rated plumbing. This is because of the additional material used for thicker sidewall and the included colorant. Undoubtedly, the schedule 80 pipes are heavier when compared to schedule 40 PVC pipes and fittings because of the thicker wall.