Young_carpenter wrote...

(BTW, I really don't know, but I'd be surprised if the plastic pipe
that's suitable for compressed air is nylon. It might be a polyethylene
or polypropylene, though.)


Air is a different property than water and most water pipes won't build up
150-200 psi (if it did it would hurt like anything when you ran the shower).

The key is in the differences in volume under pressure and under no
pressure. Under even 120 psi, water compresses very, very little. So,
when water expands due to a breach in PVC pipe, it doesn't move far
before all the pressure is released. OTOH, when gas is compressed to 120
psi, it occupies only a fraction of its zero-pressure volume. When the
pipe fails, the gas rapidly expands back to its original volume, taking
shards of PVC along for the ride.

Jim