Qualplex is used for piping drinking water in most houses these days, so it perfectly safe. Easy to work with too! Not sure how high it can take with temps, but it can certainly deal with the kind of temps you'd get from a household hot water supply.
Couldn't find much information about it on the internet, and I don't rely on the Woodie's people to get technical info.
But I like the idea of it, copper is pricey and a pain to work with, for connections and soldering.
Hmmm, seems to be difficult to find the product specifications for Qualplex on the auld Interweb allright. I see it's not recommended for solar panels because of temperatures, but it doesn't say what temperatures!