Labeling rated PVC Pipe
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schedule rated pipe
The more traditional method for labeling pipe pressure is based on the standard dimensions of steel pipe, this is called "Schedule" PVC. THe most common types of Schedule (abbreviated SCH) PVC are SCH 40 and SCH 80. When you increase the diameter of SCH pipe the strength and pressure rating begin to decrease, due to the wall thickness remaining the same.
Note that the industry standard rule is that your normal operating pressure should not exceed 1/2 of the rated pipe pressure. In other words, you shouldn't use 2" SCH 40 pipe for pressures higher than 140 PSI. This is because of pressure surges, or "water hammer", created by closing valves which can easily double the water pressure in the pipe. This rule applies to all PVC
class rated pipe
Another way of labeling the pressure rating of the PVC is with Class (abbreviated "CL"). The CL system of labeling rates the internal pressure that a pipe can take, so pipe labeled CL200 can take 200 PSI no matter the diameter of the pipe. Some of the more common types of CL pipes are CL125, CL160, CL200, CL315