The Technology Behind the Power-Pipe:
Drain-Water Heat Recovery

After space heating, water heating is the second most costly energy demand in homes, accounting for 20-30% of energy consumption. Likewise, drain-water is easily one of the largest overlooked sources of energy savings in commercial and commercial enterprises. Approximately $40 billion dollars goes down the drain in North American each year.

When warm water goes down the drain, it carries away valuable energy with it.  Ninety percent of the energy used to heat water in a home can be washed out to the sewer.  Drain-water heat recovery (DWHR) systems can re-capture some or most of this valuable energy and use it to preheat cold fresh water.  There are many ways that DWHR units are deployed in commercial and industrial installations, while there is one primary and simple method for residential installations.

Return on Investment:  Cost = Savings

The total installed cost for a DWHR unit in a home is typically between $500 and $1000 dollars. In commercial and industrial applications, the investment varies on the type and size of drain-water application. Since industrial and commercial systems run for a large portion of the day, the energy savings are often very substantial and because the size of drain-water systems are scalable, commercial and industrial systems have no limit on the size. (Federal, state and provincial tax and rebated incentives exist for many commercial, industrial and residential users)

For residential, the most accurate claim is that the savings on water heating ranges from 25% to 40%, depending upon a number of factors including efficiency of unit, how the freshwater is plumbed and water use habits.  For commercial and industrial sectors, savings can be up to 80% with short payback periods.

Paybacks vary depending upon usage.  In residential applications, the payback can typically ranges from two to six years; in commercial applications, its one to five years, and 0.4 to two years for industrial applications.

Getting Green with True Environmental Benefits

In Residential, the typical DWHR unit will reduce GHG emissions by about 200kg/person/year when displacing Natural Gas water heating. In homes with electric heating the impact can be much more because of peak load reductions and because electric water heater elements will not be on for nearly as long in homes with DWHR units.  The ideal situation to reduce GHG emissions is to take advantage of the greater water heating capacity and have the water heater turn off during the day; by doing this only low cost and low GHG-emission off peak electricity is used to heat water.  Home owners with time-of-use electricity metering would then see huge reductions in their cost to heat water.

As with any energy saving technology, the size of the initial investment and the amount of energy savings generated by drain-water heat recovery depends on the quality of the drainwater heat devise you are using. The results noted on this website are based on the patent pending Power-Pipe™ Drainwater Heat Recovery system by REI.