October 2012
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All facilities should be on the lookout for single-pass cooling, which is often a hid-
den but rather significant water use associated with certain heating, air conditioning,
and refrigeration equipment; hydraulic equipment; CAT scanners; X-ray equipment;
vacuum pumps; ice machines; and wok stoves.
Like single-pass cooling systems, cooling towers also use significant quantities of
water by design. Cooling towers dissipate heat from recirculating water that is used
to cool chillers, air conditioning equipment, or other process equipment. After as-
sessing whether single-pass cooling can be eliminated, facilities should focus next
on ensuring that the cooling tower is properly maintained to minimize the need for
make-up water. Facilities can also consider alternative sources of water for cooling
tower make-up to significantly reduce the demand for potable water.
In many cases, cooling towers are used in conjunction with chilled water systems to
remove heat by passing recirculated cold water through equipment. Chilled water
systems are often used to cool air passing through air handling units, but they can
also be used to cool a number of other systems or specific pieces equipment. Chilled
water systems and/or cooling towers can be found in relatively small facilities, such
as office buildings, schools, and supermarkets and in large facilities, such as hospitals,
office complexes, and university campuses. Energy-efficiency measures should be
used to decrease the load of the entire system to significantly reduce water used in
both chilled water systems and cooling towers.
Boiler and steam systems are used in large building heating systems for heating
water or to produce steam for industrial processes, cooking, or other operations. For
example, hospitals might have central steam systems to supply steam for steriliza-
tion, while large commercial kitchens use them to operate combination ovens, steam
cookers, and steam kettles. Other types of facilities might use boilers to supply hot
water. Returning steam condensate back to the boiler is an important first step in
improving water efficiency of boiler and steam systems.
Section 6: Mechanical Systems
of
WaterSense at Work
provides an overview of and
guidance for effectively reducing the water use of:
••
Single-pass cooling
••
Cooling towers
••
Chilled water systems
••
Boiler and steam systems
6.1
Introduction to Mechanical Systems
Single-Pass Cooling Case Study
To learn how the U.S. Environmental Protection
Agency’s Mid-Continent Ecology Division Labora-
tory in Duluth, Minnesota, eliminated single-pass
cooling and reduced its potable water use by 90
percent, read the case study in Appendix A.
