We use quite a bit of hot water mostly for showers and baths, and to wash our dishes and clothes. Unfortunately, 80-90 percent of the energy used to heat that water goes right down the drain. Now for less than $500-$700 plus installation costs, owners of single family and multifamily homes can install a drain heat recovery system to recover that heat. That means longer hot showers, saving electricity or natural gas and of course money. The payback time is about 2-3 years.

Hot Water Factoids
When we take a shower or bath, we like our water about 105 degree F. If we use hot water to wash clothes the temperature is even higher, usually 130 degree F. It takes a lot of energy to heat water to those temperatures. Don't forget the temperature of tap water entering your home ranges from 40 degrees (New York) to 70 degrees (Florida) depending on where you live and the season.

If you want to save energy and money, then don't wash clothes with warm or hot water. On average, 35 percent of your energy use goes to that alone and 90 percent of the energy cost of using the washer is used to heat the water. Cutting back on those long showers could also save energy and money too

Of course you can heat water using solar energy. That would malke sense. However, a solar hot water system may be out of reach for many people right now.  Besides that, i believe you have to make every effort to conserve energy and that includes insulating water pipes and hot water tanks first.

After doing the above, then consider recapturing some of the heat in that hot water running down the drain. You can do that with a drain or greywater recovery system like the one below which can can be installed by any licensed plumber.

How  a drain (greywater) heat recovery system works

Any hot water that goes down the drain carries away energy with it. Drain-water (or greywater) heat recovery systems capture this heat and preheat cold water entering the water heater. Tap water coming into a house usually averages 40-70 degrees F. The GFX heat recovery system manages to heat that water so that by the time it comes out of the coil it's 15 to 20 degree warmer. So how does it do it? Here's how:

1) As the picture shows, a greywater heat recovery unit is a fixed diameter pipe that has copper coils wrapped around it. There are no moving parts. The coils easily conduct heat from the copper drain pipe.

2) When hot water goes down the drain, it usually clings to the walls of the drain pipe in a thin film. When the cooler tap water in the coil runs next to it in the opposite direction, the heat in the drain warms the water in the coil. Nothing complicated about that.

Drain (Greywater) Heat Recovery Videos
Please take a look at the following videos and you'll get a better idea of the drain heat recovery systems. The first video below has Bob Villa in it. Note: it is very slow to start, so please give it a minute to run.

a) GFX Heat Recovery Unit Install in New York (Bob Villa)

b) For those who want to do this yourself or to show your plumber, see the following at Green TV.

You can install a GFX below a shower drain, but ideally it should be installed where hot water from showers, baths, dishwashers and washing machines all come together.

Resources

GFX Heat Recovery System Brochure [PDF] 
Rocky Moutain Institute Study [PDF]
Department of Energy Guide on Heat Recovery System

Disclosure: We are not affiliated or being paid by GFX Technologies.

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