the original floor was steel and worked terrific but 2 years ago we tore it up and replaced it. The company used 1/2" plastic with 2 feeder lines going into the bay. the bottom line is when the temps go below -8 the bay freezes up and you wouldnt know there is a coil in the floor. we have uped the temp to 140 and reduce flow to another bay and it is better but pretty much frozen up. Anybody have any knowledge on this matter?