PEX could be a possible alternative, but it's not as rigid as PVC and it's a bit lighter so you might want to fill it w/ something. Also, it is typically connected using a special mechanical crimp fitting, but if you're wrapping the hoop w/ tape it would probably be just fine taping it over a union connector.
PEX is available in 1/2", 3/4", and 1" sizes at most plumbing supply houses.
It's a cross-linked polyetheylene and is NOT manufactured from vinyl chloride or other chlorinated polymers.
It's pretty standard to use PEX for all the plumbing and radiant heating in houses nowadays. It's a lot easier and cheaper than running copper.
http://www.ppfahome....pex/faqpex.htmlhttp://www.ppfahome....inal_102504.pdf