Can PVC or CPVC pipe be used for compressed air lines?

PVC and CPVC pipes should not be used for compressed air lines.

Here is what the manufacturer has to say about it.

WARNING! The use of plastic piping with compressed air or gasses can result in severe bodily injury or death.

Harvel’s PVC and CPVC piping products are “rigid” thermoplastic. Harvel Plastics, Inc does not recommend using PVC or CPVC piping products for testing, transporting, and storing compressed air or gas. The compressibility of air or other gases results in tremendous amounts of stored energy, even at lower pressures. Should a failure occur in a compressed air or gas system for any reason (i.e., improper assembly, mechanical damage, etc.), the failure mode will be very dramatic due to the physical characteristics of the rigid piping in combination with the immediate release of stored energy. Under these conditions, the velocity created by rapidly escaping air and the resultant failure mode can throw shards of plastic in multiple directions (i.e., shrapnel/projectiles). This scenario creates a substantial hazard to personnel and property within the vicinity of the piping should a failure occur. Several cautionary statements and alerts against the use of rigid PVC/CPVC piping for use with compressed air or gasses are available through the Plastic Pipe Institute(PPI), American Society for Testing(ASTM), various other trade organizations, manufacturers, safety codes, as well as several State and Federal Agencies(i.e., OSHA).

Compressed air or other gasses should never be used in testing. Extreme care should be used to ensure complete venting of all entrapped air when filling the system with water or other liquids used in testing. Whether a hydraulic hand pump or available water line pressure is used, any slow build-up of gauge pressure in a completely liquid-filled line shows some entrapped air in the system. Pressure should be immediately released, and the line re-bled. Failure to do this can lead to a catastrophic failure when the decompressing gas suddenly accelerates the solid water column if a faulty joint separates.

PVC and CPVC piping systems are not recommended for compressed air lines. Improper installation and inferior cementing techniques can lead to an abrupt release of tremendous stored energy. Shattering of pipe and fittings is then apt to occur at directional changes and at the point where the system is rigidly restrained due to instantaneous whipping action imparted by the escaping air. Due to the stress, internal surface cracks can be initiated, which will tend to propagate and cause shattering hairline or pinhole cracks over time. There is also evidence that certain additives to system lubricants will initiate internal stress cracking, leading to similar failure over extended periods.