Tired of cold showers? Get a GreenFoX!

Drain Water Heat Recovery (DWHR)

*  Easy to install  *  Maintenance free  *  Lower water heating bill  *


The GreenFoX is not a water heater but an easy add-on to give it a boost and increase your water heater efficiency rating.  It will reduce the workload, give it a faster recovery time, and conserve energy!

DWHR works with a traditional tank or tankless water heater, solar, geothermal heat pump or any other type of water heating system. Whether you’re a homeowner, business owner, or facility manager there is a GreenFoX for you! 

You can run multiple showers, and other appliances, at the same time without losing pressure or getting a blast of cold water.  An instant fix for tankless water heaters that have a hard time keeping up with demand in cold water regions.

Because of gravity, the GreenFoX works for you every time hot water goes down the drain. The payback on a DWHR system is as quick as 2 years.  This depends on how many people are in your household, how many showers each day, the type of heating fuel used, and groundwater temperatures.

Example of hot and cold water temperatures with a GreenFoX DWHR
Example of hot and cold water temperatures with a GreenFoX DWHR
Which drain water heat recovery unit to buy?

Which DWHR For Me?

The size of the GreenFoX and the rated efficiency is based on the number of people in the household or on the amount of hot water a facility uses. For the best return on investment, we recommend the 42” unit for households of 4 or fewer people and the 48” for 5 or more people. The 36” units are great for households with 3 or fewer people, or for limited clearance and crawl spaces.  

Before and after a drain water heat recovery unit is installed.

DWHR Placement and Installation

The heat exchanger becomes part of the drainage stack by replacing a vertical section of the drain line, usually in your basement. The outside coil becomes part of your fresh water supply line.  It can be installed with any combination of drainage pipe and fresh water piping. 

Measurements for a GFX installation

DWHR Sizing

A. Determine size of the drain diameter (2”, 3” or 4” is normal)

  • Requires two (2) no-hub connectors; copper to ABS, PVC, or cast iron

B. Find longest section of available vertical space in the main drain line

  • Basement, first floor or crawl space

C. Use ¾” connections for the cold-water supply

  • shark bites or copper fittings


For larger residences and commercial uses, units can be connected


DWHR Maintenance

Since the diameter of the GreenFoX is the same as the existing drain, there is no clogging or build up.  There are no moving parts or required maintenance.  And since it is all copper, it will last the lifetime of your plumbing and is 100% recyclable at the end of its useful life, in about 30 years or so.


Code Compliance

Intertek ETL/Warnock Hersey 3rd party testing and safety certification
IAPMO PS 92 Standards for Heat Exchangers
IAPMO 2012 Green Plumbing and Mechanical Supplement Code  Section 606.0
CSA B55.1 Performance Standard
CSA B55.2 Safety Standard

2015 International Code Council
Energy Conservation Code
 Section C404.8,  Section R403.5.4
 Chapter 4 [CE] Commercial Energy Efficiency
 Chapter 4 [RE] Residential Energy Efficiency
Green Construction Code Section 607.5
 Chapter 6 Energy Conservation, Efficiency
 and CO2 Emission Reduction
Residential Code Section N1103.5.4 (R403.5.4)
 Chapter 11 [RE] Energy Efficiency 


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