Compressed air or other gases should never be used for pressure testing plastic plumbing systems. These systems should be tested by hydrostatic means. This is a life safety issue, not a product performance issue.

PPFA's policy is that only hydrostatic pressure testing of plastic piping systems be conducted.

1.) One exception to this policy involves ordinary trap seal pull testing, where a completed DWV system is air tested with all of its traps filled with liquid water, and the trap seals are tested with pressure of vacuum in the normal operational pressure range of the system, typically between one and two inches of water column. Precautions must be taken to ensure that traps do not freeze before or during the testing.

2.) Another exception is for plastic piping systems specifically designed for use with compressed gasses. In these cases the manufacturers' recommendations must be strictly followed for installation, testing and use of the systems.

Commentary:  

There is no difference between static test pressures whether they are derived from gasses or water. Pressure testing with water, or hydrostatically, is intrinsically safer than testing with compressed gasses. Because gasses are compressible, they can store large amounts of potential energy. Should a test plug, fittings or temporary cap separate or a section fail for any reason while undergoing an air pressure test, the potential energy release is rapid and grievous injuries could result.

The manufacturer should be contacted if there is any doubt as to how a specific system should be tested.

NOTE:
This PPFA User Bulletin is designed to provide guidance in achieving the efficient, effective and informed use of plastic pipe. The suggestions and advice contained in this Bulletin are offered merely to provide plastic pipe users with a general frame of reference. Because specific situations may, and often do require special treatment, the suggestions and advice are obviously not universally applicable. Therefore, the user should carefully assess the requirements of his specific situation before making practical application of anything contained in this publication.