I have just finished the hydronic heat piping for the new house and
had a couple hundred feet of 1/2" PEX left over from the 3000 feet
purchased. The building inspector was giving me conflicting test
requirements. The installation manual says 60 psi air test and the
inspector wanted a 100 psi hydrostatic test so I got on the phone to
the manufacturer. They sent out an intallation engineer who told me
the PEX could handle a 300 psi hydrostatic test. I suggested it might
be good for shop air in that case and he said it would be just fine.
Remember this PEX is a Polyethylene compound and pretty flexible so it
won't shatter if ruptured. Its not cheap at $.52/ft in 1000 ft rolls
but what can you do with the remnants when the heating system is in.
BTW I never did perform the hydrostatic test as I hadn't quite
finished purging the air from the six water circuits when the
inspector arrived. The system had held steady on 100psi air pressure
for 10 days though so he & I were pretty confident there were no
leaks. The system has seven ball valves, seven unions, a silver
soldered copper manifold and about 20 other joints in it. Anybody got
a shop air system of this complexity that DOESN'T leak. All joints are
above the slab so repair was doable but not necessary.
Leigh@MarMachine