What Types of Pipes Does my Solar Thermal System Need?
It's important to make one thing very clear when discussing piping materials for a solar thermal installation: copper or stainless steel are currently the only sensible choices.
It may be tempting to try to use a flexible material like rubber or Pex, but it won't work: there's a very good chance you'll have to replace all your piping within the first year of operation because it simply cannot withstand the constantly high operating temperatures of the system.