Hydronic radiant systems heat a home by circulating hot water through tubing placed in evenly spaced layouts under the finished floor of the home. There are limits to the length of a tube that water can be efficiently pumped through. It is accepted hydronic practice to limit the length of any single circuit of 1/2″ tubing to less than 350 feet. Each of these circuits is called a loop. Most homes will have their floor area heated by a varying number of these loops.