How does GreenFoX work?

GreenFoX works on the principle of Gravity Film Xchange.

GreenFoX is based upon a natural phenomenon where surface tension and gravity cause falling films of drain water to spread and cling to the inner walls of vertical drainpipes. This is the principle of Gravity Film Xchange.

When water falls down a vertical section of the drain pipe, it clings to the inner surface in a very thin film. The heat from this film is easily and efficiently transferred to the cold water circulating in the unit around the outside of the drain pipe.

The tension is strong enough to cut film speeds to about 1.3-3.9 feet per second and hold their thickness to 12-27 mils at 0.44-3.1 gpm, respectively. This tension enables very high rates of heat transfer whenever hot water enters a GFX and cold water is rerouted to simultaneously flow up its coil. It incorporates equal flow rates on both sides of the heat exchanger for optimum efficiency.

GreenFoX’s unique falling film coil and tube design, a double-walled, vented copper heat exchanger, yield transfer coefficients 2 to 4 times that of a usual shell and tube heat exchanger.

Double-wall vented means there is no soldering or brazing between the drain pipe and the coil, which is a requirement for use with any potable water system to prevent cross-contamination of drinking water by sewage, in the event a sewer line becomes clogged and a cold water main fails.

The GFX has no moving parts, just a tight coil of 1/2 inch diameter copper tubing around a 3-inch copper pipe, or a 3/4 inch diameter copper tubing around a 4-inch copper pipe. The units are between 2 and 5 feet tall and replace a section of the vertical drainpipe.

Plumbing Codes and Certifications

GreenFoX is ETL certified