Radiant Floor Tubing
Older radiant floor systems used either copper or steel tubing embedded in the concrete floors. Unless the builder coated the tubing with a protective compound, a chemical reaction between the metal and the concrete often led to corrosion of the tubing, and to eventual leaks. Major manufacturers of hydronic radiant floor systems now use cross-linked polyethylene (PEX) or rubber tubing with an oxygen diffusion barrier. These materials have proven themselves to be more reliable than the older choices in tubing. Fluid additives also help protect the system from corrosion.
There have been recent reports of problems with rubber tubing produced by one chemical manufacturer. Leaks develop at the metal connections or fittings, and in some cases the tubing becomes rigid and brittle. It is still not clear what causes this problem, but theoretically excessively high water temperatures may be to blame. Tightening connections and clamps only temporarily fixes the leaks. Remember this problem only concerns a specific brand of rubber tubing. It does not have anything to do with the PEX tubing, which has performed very reliably for many decades.
Since the price of copper tubing is considerably lower now than several years ago, it is again gaining some popularity because of it’s superior heat transfer abilities over plastic-based tubing.
Source:http://www.radiant-heat-floor-methods.com/radiant-heat-tubing.html