Greenpeace is against PVC because of the vinyl chloride potential. Polybutylene has been dumped. The new plastic is the PEX, reputedly good to 260F. Many manufacturers are recommending its use, especially for radiant heat. I know of one manufacturer making straight 20 foot lengths of PEX with a sealed internal aluminum layer to make it take a set. Are there any bad stories about PEX? Why isn’t it made in sizes larger than 1-inch(yet?)?