When installing PEX tubing for radiant heat, you must be careful not to make the individual loops too long. If there is too much distance between where the water gets heated and the end of the loop where runs under your floors, you run the risk of allowing it to cool to the point where it will not actually be heating anything. As a rule of thumb, for 1/2" tubing, be sure that no loop is longer than 300 feet. If you purchase tubing that is longer than 300 feet, you will need to cut it into multiple lengths before installation.
PEX pipe, and PEX for radiant floor heat can be found at www.supplyhouse.com
