Recently I visited a supply house where they specialize in air compressors and air delivery systems for commercial and industrial installations.
They now have a new (to me, at least) a flexible ALUMINUM pipeing system. Color of the pipe is blue. All connectors are "push-on" type. 1/2 in. and 3/4 in.
The pipe is not PEX.
So, you might look around your area for such a supply house and ask about the new stuff.
I do not recommend using PVC. As the PVC gets some age, it seems to lose flixibility and will shatter, instead of bending or simply cracking. If in doubt, remove a piece of "aged" PVC and do a sample bending of the pipe. Becareful of flying debris.
Only problem with black pipe might be the collection of moisture and rust inside the pipe.
Water drains should be installed according to the Codes.
Hope this helps.
PS: Like all new products, I will wait awhile and see how that new flexible aluminum holds up.
Meantime my rubber hose system will work for me.