Save Some Heat from Your Used Hot Water

Posted on Tuesday, May 20th, 2014 by Nathan Weinstock

There’s a lot of buzz around energy savings in a house.  When I do my home inspections here in Ottawa, I pay close attention to how well the house provides reliable energcopper-coil-s-90x300y performance.  The main focus is generally the heating system and the building insulation.  These are first and foremost in most people’s minds.  What is less well known is the hot water system.

You spend a lot of money heating water in your house, for showers, laundry, and dish washing.  Water heating is easy and generally quite reliable.  But it is also quite costly.  Water carries a significant amount of energy so it takes a lot of energy to heat up.

Once it is hot, the water goes about its business cleaning you, your clothes, or your dishes.  After the hot water has done its job, away it flows, down the drain.  What a shame, losing all that heat, just like that.

That is where a drain water heat recovery (DWHR) system can help.  Such a system will recover some of the thermal energy that’s just thrown away down your drain.  The system is a water to water heat exchanger designed for use with drain water.  A drain

water (or greywater) heat recovery system captures the energy from the hot water leaving in the drain and uses it to preheat cold water entering the water heater.

The way a drain water heat recovery system works is quite innovative and elegant.  This technology is simple, long-lasting and has no moving parts.  The cold water coming into your house runs through a series of copper coils that are tightly wrapped around your drain stack.  (See the picture.)
When someone takes a shower, does laundry, or runs the dishwasher, the warm water runs down the drain.  As it goes down the drain, it transfers its heat through the copper walls of the drain water heat recovery unit.  This warms the cold water coming into the house, before it goes into the water heater.  The heat is transferred, but the drain water never mixes with the fresh, and your water heater uses less energy.

By recovering some of the heat that would be lost down your drain, you will use less new energy to heat your hot water.  Not only do you save money, but you also reduce your carbon footprint.  Less energy consumed means less greenhouse gas produced.  It’s simple and you will enjoy the savings for many years to come.