1. • DWHR Basics and History (Gary Proskiw,
Proskiw Engineering Ltd.)
• Installation Considerations and Procedures
(Gio Robson , prairieHOUSE Performance Inc.)
• Manitoba Hydro Programs (Allison Lund
Manitoba Hydro)
Drainwater Heat Recovery
Systems (DWHR)

2. • What are they?
• What are their benefits?
• Have they ever been used in Manitoba?
• How do they work?
• How are they installed?
• Why should you care?
DWHR Basics and History

3. • DWHR Systems are simple water-to-
water heat exchangers which recover a
portion of the energy in a home’s
wastewater and use it to preheat
the incoming cold water – thereby
reducing the Domestic Hot Water
Heating (DHW) load.
What Are They?

4. • About 90% to 95% of all new homes in Manitoba
use electric hot water tanks.
• Average annual DHW energy use : 3400 kWh/yr,
which costs the homeowner about $250 /yr.
• This represents about 15% to 25% of the home’s
total energy use).
Some Basic Facts About DHW
Heating In Manitoba

5. • Higher insulation levels, improved airtightness,
high performance windows, better heating
systems, HRV’s, etc. have all reduced the space
heating load of our houses.
• But little has been done to reduce the DWH load.
Some Basic Facts About DHW
Heating In Manitoba (con’t)

6. • Reduced energy consumption
• Reduced energy costs
• Longer showers – even with electric tanks!
• Reduced environmental impact
• Extends the life of the water heating elements
or burner
• Faster tank recovery
• Improved output capacity for instantaneous water heaters
Benefits of DWHR Systems

7. A Little Bit of History
• Over the years, many people have experimented with
DWHR systems.
• In 1978, Electrohome developed a heat pump-based
DWHR system – which never went into production.
A good example of a
bad example!

8. A Little Bit of History (con’t)
• Most early attempts to develop a
workable DWHR unit incorporated
some form of thermal storage.
• But storage is problematic:
(leaks, smells, maintenance, need
for segregated plumbing lines,
lost floor space and the $$$$$).
• Today, no one uses thermal storage
for residential DWHR systems.

9. A Little Bit of History (con’t)
• The first, known, commercially
available residential DWHR system
– known as the GFX – was
introduced in 1997.
• In 1998, 18 GFX units were installed
in a variety of new and existing
houses under a Manitoba Hydro-
sponsored research program. They
were monitored for a total of 26.5
house-years.

10. The 1998 Manitoba Hydro
Study.....What Was Learned
• The DWHR systems reduced the hot water load
by an average of 16%, although significant
variations occurred among houses.
• However, during showers the recovery efficiency
increased to between 30% (high flow rate) and
54% (low flow rate)
• No water leaks were reported with any of the
systems (or have been reported since).
• No smells or other problems were reported.

11. The 1998 Manitoba Hydro
Study.....What Was Learned (con’t)
• Homeowner satisfaction was very high. Many
felt that their supply of hot water had increased,
in some cases substantially.
• More showers, or showers of greater duration,
could take place without a significant reduction
in water temperature.
• Further, when the supply of hot water was
approaching depletion, the temperature drop-
off was slower and much less pronounced.

12. The 1998 Manitoba Hydro
Study.....What Was Learned (con’t)
Ideal residential DWHR applications:
• Big families
• Expensive fuel source
• High DHW consumption
• Poor water heating efficiency
• Need for two DWH tanks

13. The 1998 Manitoba Hydro
Study.....What Was Learned (con’t)
0
1000
2000
3000
4000
5000
6000
7000
0 2 4 6
DHWUse(kWh/yr)
Number of People

14. So, How Do DWHR Systems Work?
• All commercial DWHR systems
designed for houses utilize the Coanda
effect, which is the tendency of a fluid
jet to be attracted to a nearby surface.
The principle was named after
Romanian aerodynamics pioneer
Henri Coanda
• Wastewater flowing down the pipe
tends to cling to the walls of the inner
pipe – not to the interior of the pipe.
• This greatly enhances heat transfer!

15. Batch vs. Simultaneous Flows
• Batch flows: the drainwater and fresh water flows
DO NOT occur at the same time (baths, washing
machines, automatic dishwashers). BAD
• Simultaneous flows: drainwater and fresh water flow
DO occur at the same time (showers and some
manual washing). GOOD
• To capture energy from batch flows, thermal
storage is needed (which is a problem).
• In most houses, roughly 1/3 of the DHW load is
simultaneous flows and 2/3 batch flows.

16. DWHR units use a “double-wall
heat exchanger” to separate the
waste and fresh water streams.
Contamination would require:
1. Failure of the inner pipe and
2. Failure of the outer tubing and
3. Failure of the mains water
pressure and
4. No one noticing.
But, what about
cross-contamination?

17. Basic DWHR Installation

18. Some DWHR Tidbits:
• Over 200 different DWHR models are listed
in the data base maintained by Natural
Resources Canada.
• Three Canadian manufacturers:
(Power Pipe, Watercycles Energy
Recovery Inc. and EcoInnovation
Technologies Inc.)

19. Some DWHR Tidbits (con’t):
• The longer the unit, the more heat is
recovered.
• Lengths range from 24” to 120” (0.6 m to
3.1 m). Available diameters: 2”, 3” and 4”
(51, 76 and 102 mm).
• Annual energy savings range from
1100 to 2650 kWh/yr
(worth $80 to $200 per year).

20. EQUAL FLOW UNEQUAL FLOW COLD SIDE ONLY UNEQUAL FLOW HOT SIDE ONLY
Installation Configurations

21. Section 9.36
Energy Efficiency
• In 2014, the Part 9 Sub-Committee on Energy & Water
Efficiency of the Manitoba Building Standards Board
completed its review of the recently published
“Section 9.36 Energy Efficiency” of the NBC.
• This included the recommendation that DWHR systems be
mandatory for all new construction in Manitoba except for
houses with crawl space or slab-on-grade construction.