Root Zone Heating Systems for Greenhouses
A typical hot water root zone heating system contains a water heater or boiler, circulating pumps, piping, and controls.
The least expensive pipe is polyethylene, which is available in 100-foot and 400-foot rolls. Select a pipe made of virgin plastic rather than one having reconstituted resins. It should have a pressure rating of at least 100 psi. Polyethylene will take temperatures up to 130 degrees F. Most growers who use poly pipe operate with a water temperature of 100 degrees F. to provide
70 to 75 degrees F. soil temperature. Nylon fittings and stainless clamps will minimize the potential for leaks. Fittings that are buried below ground should have double clamps.
Semi-rigid polyvinyl chloride (PVC) is also low cost. It is available in 10-foot and 20-foot lengths which makes installation easy. Fittings are connected with pipe cement.
Commercially available systems are available that use EPDM rubber tubing either as single tubes or as two or four tubes attached to a rack. Diameters of 3/8 inch or