I thought PVC was dangerous to use for air lines because if it broke could throw splinters.
Liquids do not compress losing it's energy when a rupture occurs. Gases are compressible
and under pressure release energy returning to the uncompressed state. Tubing used for
compressed gases has to be rated for that use. OSHA does not allow PVC/CPVC for use in
shop use in compressed air situations. If so it has to encased. There have been many injured
using PVC as Spud guns.
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When I worked for irrigation business in early 90's spud guns were very popular. Kids coming
in all the time wanting to buy parts and pieces to build spud guns. The owner--had a policy
that any time someone buying certain diameters/lengths of pvc along with only a few
distinct pieces were more than likely about 99% of the time building spud guns. He allowed
no sales at that point-using the {Right to refuse service to anyone}. For the fact it was known
that many were injured by exploding PVC. He didn't want anyone having the ability to come
back on him.