text: When a pipe is welded or bent the most common method to inspect blockages, misalignment, ovality, and weld bead dimensional conformity is to pass a round ball through the pipe coil or circuit. If the inner pipe dimension is to be measured then the weld bead should be subtracted, if welding is applicable. Typically, the clearance tolerance for the ball must not exceed . Allowable ovality of any pipe is measured on the inside dimension of the pipe, normally 5% to 10% ovality can be accepted. If no other test is conducted to verify ovality, or blockages, this test must be seen as a standard requirement. A flow test can not be used in lieu of a blockage or ball test. See pipe dimensional table, Specification ASME B36.10M or B36.19M for pipe dimensions per schedule.
  Stainless steel pipe is most often available in standard weight sizes (noted by the S designation; for example, NPS Sch 10S). However stainless steel pipe can also be available in other schedules.
  Both polyvinyl chloride pipe (PVC) and chlorinated polyvinyl chloride pipe (CPVC) are made in NPS sizes.