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Doing More With Less - Passive
Heat Recovery Works

There are simple, low-tech ways to make use of heat that you already have. This means that a tankless water doesn’t have to work near as hard to deliver hot water. This translates into less energy used and greater output.

It's almost certain that energy prices will rise and almost everything in the near future will be powered by electricity, including home heating, hot water and cars.

Method 1
Wastewater heat recovery
A lot of wastewater is hot water that is traveling through a pipe on the way out of the house. The Dept of Energy estimates that 350 billion kWh of hot water goes down the drain like this each year.

A simple heat recovery installation can recoup a good portion of that wasted heat. This heat recovery unit replaces a section of the drainpipe with a copper pipe wrapped in another copper pipe.

The outer pipe, carrying fresh water, picks up the heat and delivers it direct to the tankless heater. This could increase the temperature of water entering the heater by as much as 60 percent. The estimate is the greater the difference between ground water temperature and heated temperature the greater the efficiency of the recovery unit.

There are several brands of drain water heat recovery pipes and they range in price from $400 to $1,500. A device like this could eliminate the need for larger a model heater and provide more hot water.

Method 2
Passive water storage
If you have your water heater in a heated part of the house (basement or utility room) then you can make use of the ambient temperature to preheat water flowing into the heater. This an economical way to cut energy cost by 10-20 percent and boost flow rate.

Commercial plastic models for drinking water storage are available from RV to 1000-gallon size. Using your old water tank is an option if it is still serviceable - turn the power off and remove the insulation is all that’s necessary. A drip pan would be a good safety precaution.

These two add-on should be considered with any new or upgraded hot water system, since they are relatively inexpensive and need no power supply. Note: Bosch and perhaps some other manufacturers caution against preheating tankless water above 80 F degrees.

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