WaterSense
at Work

Laboratory and Medical Equipment

7.2 Vacuum Pumps

Best Management Practices for
Commercial and Institutional Facilities

*

EPA

WaterSense

March 2024


-------
WaterSense® is a voluntary partnership program sponsored by the U.S. Environmental
Protection Agency (EPA) that seeks to protect the nation's water supply by transforming
the market for water-efficient products, services, and practices.

WaterSense at Work \s a compilation of water efficiency best management practices
intended to help commercial and institutional facility owners and managers from multiple
sectors understand and better manage their water use. It provides guidance to help
establish an effective facility water management program and identify projects and
practices that can reduce facility water use.

An overview of the sections in WaterSense at Work is below. This document, covering
water efficiency for vacuum pumps, is part of Section 7: Laboratory and Medical
Equipment. The complete list of best management practices is available at
www.epa.gov/watersense/best-management-practices. WaterSense has also developed
worksheets to assist with water management planningand case studies that highlight
successful water efficiency efforts of building owners and facility managers throughout the
country, available at www.epa.gov/watersense/commercial-buildings.

•	Section 1. Getting Started With Water Management

•	Section 2. Water Use Monitoring

•	Section 3. Sanitary Fixtures and Equipment

•	Section 4. Commercial Kitchen Equipment

•	Section 5. Outdoor Water Use

•	Section 6. Mechanical Systems

•	Section 7. Laboratory and Medical Equipment

•	Section 8. Onsite Alternative Water Sources

EPA 832-F-23-003
Office of Water

U.S. Environmental Protection Agency
March 2024

This document is one section from WaterSense at Work: Best Management Practices for Commercial and
Institutional Facilities (EPA-832-F-23-003). Other sections can be downloaded from

vwwv.epa.gov/watersense/best-management-practices. Sections will be reviewed and periodically updated
to reflect new information. The work was supported under contract 68HERC20D0026 with Eastern Research
Group, Inc. (ERG).

March 2024

i


-------
Laboratory and Medical Equipment
Vacuum Pumps

WaterSense

Overview

Laboratories, medical facilities, and dental offices use vacuum pumps to collect waste
gases, liquids, or debris from a vessel or enclosure. These vacuum pump systems range in
size, depending on whether they are used to supply a vacuum to several rooms or for point-
of-use. Dental offices' pumps range from 1.0 to 4.0 horsepower (hp), while a central
vacuum pump in a medical facility can be5.0to2Q.Q hp.1 Vacuum pumps can use water in
two ways: to cool the pump and to create the vacuum seal in the rotating equipment,
which generates the vacuum.

Generating the Vacuum

Vacuum pumps can either be "dry" or
"wet"—based on how the vacuum seal
is generated within the pump. Dry
pumps do not use water to generate the
seal for the vacuum. Instead, they
create vacuums with turbines (i.e., fans)
or use positive displacement (e.g., vane
pumps, claw pumps, piston pumps).

Wet pumps can be classified as either
aspirators or liquid-ring vacuum pumps.

In an aspirator, fluid (often water) flows
through a narrowingtube, and a

vacuum is generated by the Venturi	Liquid-ringvacuum pumps

effect. Water is used once and

discharged to the drain, making the process very water-intensive. Due to their simple
operation, water aspirators might be found most often in high school and college
laboratories for educational purposes and are used infrequently. Since liquid-ringvacuum
pumps are more common in commercial and institutional facilities, aspirators are not the
focus of this section. If a facility has a water aspirator that is used frequently, it should
consider replacing it with a dry, air-cooled vacuum pump as discussed below.

Liquid-ringvacuum pumps use a closed impeller that is sealed with water or other
lubricants such as oil to generate the vacuum. The most common type of wet pump uses
waterto form a moving cylindrical ring inside the pump casing. In these pumps, the

1 East Bay Municipal Utility District (EBMUD). 2008. WaterSmart Guidebook—A Water-Use Efficiency Plan
Review Guide for New Businesses. Page M ED2. www.ebmud.com/water/conservation-and-
rebates/commercial/watersmart-guidebook.

March 2024

1


-------
WaterSense at Work

Vacuum Pumps

vacuum is created by the changing geometry inside the pump casing as the impeller and
liquid ring rotate. As the vacuum seal water rotates with the pump, it gains heat and
gathers impurities from gases collected by the vacuum system.

In the simplest liquid-ring vacuum pump systems, the seal and cooling water are
continuously discharged and replenished with fresh water to dissipate heat and remove
impurities. Water requirements for both creatingthe vacuum and cooling the equipment
range from 0.5 to 1.0 gallons per minute (1.9 to 3.8 liters per minute) per hp.2 To save
water, these pumps can be equipped with a partial orfull recovery and recirculation
system. In the full recovery system, all the seal water is recovered from the discharge side
of the pump, passed through a heat exchanger, and reused for sealing and cooling. A small
amount of recycled water is discharged to remove impurities, and the system is
replenished with make-up water. Since it is designed to be self-contained and almost fully
recirculate seal water, this full configuration recirculation system is estimated to reduce
water use by nearly 100 percent.3

Partial recovery and recirculation systems recirculate part of the sealing water. Make-up
water is added to ensure that impurity concentration is not too high. In these systems,
consideration should be made to avoid heat build-up in the pump. Partial recovery
systems can reduce water use by about 50 percent.4

Cooling the Vacuum Pump

Vacuum pumps can be water-cooled or air-cooled. Either wet or dry vacuum pumps can
use waterto cool the system. Water-cooled vacuum pumps use single-pass cooling or
recirculated cooling. In single-pass cooling, water passes through the pump only once for
cooling, then is discharged directly to the drain. A recirculated cooling system, on the other
hand, passes the majority of cooling water through a heat exchanger, and the coolingwater
is reused. If the coolingwater does not come in contact with the vacuumed gases or other
impurities, it can be recirculated by connectingthe pump to a larger building system
chilled water loop or cooling tower water loop to remove the heat load. Air-cooled vacuum
pumps use ambient air, rather than water, to remove the heat load from the vacuum pump.

2	Ibid.

3	California Urban Water Conservation Council (CUWCC). December 2012. Water Use in Vacuum Pump
Systems & Viability for a Water Conservation Best Management Practice in California. Page 7.
https://calwep.org/wp-content/uploads/2021/03/Water-Use-in-Vacuum-Pump-Svstems-PBMP-2012.pdf.

4	Ibid., Page 6.

March 2024

2


-------
WaterSense at Work

Vacuum Pumps

Operation, Maintenance, and User Education

For optimum liquid-ringvacuum pump efficiency, consider the following tips:

Claw Technology Eliminates Water Use
While Reducing Energy and Maintenance

Some more energy-efficient vacuum systems
use a claw technology to generate a vacuum.
This technology incorporates two "claws" that
rotate in opposite directions but do not come
in contact with one another. Air is drawn in
through an inlet and is compressed by the
rotation of the claws, creating a pressurized
air pocket. When the air pocket approaches
the exhaust line (again, via the rotating claw
movement), it leaves the vacuum chamber at
a higher velocity and generates the vacuum.
See the figure below. This technology does
not require the use of oil or water and is
typically lower maintenance.

Turn off the pump when it is not in
use or needed.

Ensure that the vacuum pump is set
according to manufacturer
specifications and is being operated
in accordance with manufacturer-
recommended control schemes to
discharge only the amount of water
necessary to remove impurities and
cool the vacuum pump.

Periodically check the vacuum
pump's operational control
schemes, if available, to ensure
optimum efficiency (e.g., timers,
float-operated switches, total
dissolved solids controllers that
initiate discharge and make-up
water).

Retrofit Options

If the facility is usinga liquid-ringvacuum
pump that continuously discharges water,
thefacility can consider equippingthe
pump with a full recovery and recirculation
system to recover and reuse nearly 100
percent of the seal water.5 The facility
should consider the impurities gathered
within the pump and other characteristics
of the waste being removed when
evaluatingwhether a full recovery and
recirculation system is appropriate. A
partial recovery and recirculation system
could also be considered, and the facility could reduce water use by an estimated 50
percent.6 If either recovery and recirculation system option is installed, ensure that it is

Source: U.S. Department of Energy (DOE), Federal
Energy Management Program (FEMP). 2011. Water
Efficiency Improvements at Various Environmental
Protection Agency Sites.
www.nrel.gov/docs/fy11 ostiZ48950.pdf.

5	Ibid., Page 7.

6	Ibid., Page 6.

March 2024

3


-------
WaterSense at Work

Vacuum Pumps

properly maintained per manufacturer instructions so that impurities are removed and
hard water deposits do not remain in the system.

If the facility has any other type of vacuum pump that is cooled with single-pass, non-
contact cooling water, a heat exchanger can be added, or it can be connected to a larger
building system chilled water loop or cooling tower water loop. See WaterSense at Work
Section 6.2: Single-Pass Cooling at www.epa.gov/watersense/best-management-
practices for more information.

Replacement Options

When purchasinga new vacuum pump or replacing older equipment, facilities should
choose a non-lubricated, dry vacuum pump that is air-cooled unless fire and safety codes
for explosive, corrosive, or oxidative gases require a liquid-ring pump. Although they might
be more expensive, dry, air-cooled vacuum pumps can be about 30 percent more energy-
efficient than water-cooled or liquid-ring vacuum pumps since they do not have to pump
water along with air.7

Dental facilities should note that new vacuum systems—wet or dry, and regardless of the
type of cooling system—need to add amalgam separators and follow best management
practices established by the American Dental Association to comply with EPA regulations
to prevent mercury contamination in water bodies.8

Savings Potential

Retrofitting existing liquid-ringvacuum pumps with full or partial recovery and recirculation
systems can result in significant water savings, while replacing existing water-cooled
and/or liquid-ringvacuum pumps with air-cooled, dry vacuum pumps can entirely
eliminate water use and result in energy savings as well.

To estimate facility-specific water savings and payback, use the following information.
Vacuum Pump Retrofit

Liquid-ring pumps that utilize water to create a vacuum can be retrofitted to recirculate
sealing and cooling water rather than dischargingto the drain.

1 Ibid., Page 7.

8 U.S. Environmental Protection Agency (EPA). Dental Effluent Guidelines, www.epa.gov/eg/dental-effluent-
guidelines.

March 2024

4


-------
WaterSense at Work

Vacuum Pumps

Current Water Use

To estimate the current water use of an existing vacuum pump, identify the following and
use Equation 1:

•	Flow rate of the discharged water from the existing vacuum pump.

•	Average daily use time.

•	Days of operation per year.

Equation 1. Water Use of Vacuum Pumps (gallons or liters per year)
= Vacuum Pump Discharge Flow Rate x Daily Use Time x Days of Operation

Where:

•	Vacuum Pump Discharge Flow Rate: Gallons (or liters) per
minute

•	Wash Processes per Day: Minutes per day

•	Days of Operation: Days of vacuum pump operation peryear

Water Savings

Full water recovery and recirculation systems can reduce water use by nearly 100
percent,9 while partial systems can reduce water use by approximately 50 percent.10 To
calculate water savings that can be achieved from retrofitting an existingvacuum pump,
identify the current water use of thevacuum pump as calculated using Equation 1 and use
Equation 2, using 99 percent savings for a full system and 50 percent for a partial system.

Equation 2. Water Savings From a Vacuum Pump Recovery and Recirculation System

Retrofit (gallons or liters per year)

= Current Water Use of Vacuum Pump x Percent Savings

Where:

•	Current Water Use of Vacuum Pump: Gallons (or liters) per
year

•	Savings: Percent

9	cuwcc, op. cit.

10	Ibid., Page 6.

March 2024

5


-------
WaterSense at Work

Vacuum Pumps

Payback

To calculate the simple payback from the water savings associated with retrofitting an
existing vacuum pump, consider the equipment and installation cost of the retrofit
recovery and recirculation system, the water savings as calculated using Equation 2, and
the facility-specific cost of water and wastewater.

The facility should also consider the energy impact of the vacuum pump retrofit. The
recovery systems might use energy, which can affect the payback period and cost-
effectiveness.

Vacuum Pump Replacement

Many existing liquid-ring vacuum pumps can be replaced with dry vacuum pumps that are
air-cooled rather than water-cooled. This replacement entirely eliminates the water used
to create a vacuum and coolthe vacuum pump, and these pumps are also more energy-
efficient.

Current Water Use

To estimate the current water use of an existing vacuum pump, use Equation 1.

Water Savings

To calculate water savings that can be achieved from replacing an existing vacuum pump,
identify the current water use of the vacuum pump and the water use of the vacuum pump
after replacement (using Equation 1) and input these values into Equation 3 below. If an
air-cooled, dry vacuum pump is selected as the replacement model, water savings will be
equal to the water use of the vacuum system being replaced.

Equation 3. Water Savings From a Vacuum Pump Replacement (gallons or liters per

year)

= Current Water Use of Vacuum Pump - Water Use of Vacuum Pump After

Replacement

Where:

•	Current Water Use of Vacuum Pump: Gallons (or liters) per
year

•	Water Use of Vacuum Pump After Replacement: Gallons (or
liters) per year

March 2024

6


-------
WaterSense at Work

Vacuum Pumps

Payback

To calculate the simple payback from the water savings associated with replacing an
existing liquid-ringvacuum pump with an air-cooled, dry vacuum pump, considerthe
equipment and installation cost, the water savings as calculated using Equation 3, and the
facility-specific cost of water and wastewater.

By replacing a water-cooled or liquid-ringvacuum pump with an air-cooled, dry pump,
facilities should also considerthe impact on energy use. Dry vacuum pumps can be about
30 percent more energy-efficient than water-cooled or liquid-ringvacuum pumps.11 The
energy use will also affect the payback time and replacement cost-effectiveness.

Additional Resources

American Dental Association. August 2022. Amalgam Separators and Waste Best
Management, www.ada.org/resources/research/science-and-research-institute/oral-
health-topics/amalgam-separators.

California Urban Water Conservation Council. December 2012. Water Use in Vacuum
Pump Systems & Viability for a Water Conservation Best Management Practice in
California. https://calwep.org/wp-content/uploads/2021/03/Water-Use-in-Vacuum-
Pump-Systems-PBMP-2012.pdf.

East Bay Municipal Utility District. 2008. WaterSmart Guidebook—A Water-Use Efficiency
Plan Review Guide for New Businesses. Pages MED1 -2.

www.ebmud.com/water/conservation-and-rebates/commercial/watersmart-guidebook.

International Institute for Sustainable Laboratories (I2SL) and U.S. Environmental
Protection Agency (EPA). May 2022. Best Practices Guide: Water Efficiency in Laboratories.
www.epa.gov/system/files/documents/2022-06/ws-l2SL-Laboratory-Water-Efficiency-
Guide.pdf.

U.S. Department of Energy (DOE), Federal Energy Management Program (FEMP). March
2011. Water Efficiency Improvements at Various Environmental Protection Agency Sites.
www.nrel.gov/docs/fy11osti/48950.pdf.

11 Ibid., Page 7.

March 2024

7


-------
Disclaimer

This document was prepared as an account of work sponsored by the United States Government.
While this document is believed to contain correct information, neither the United States
Government nor any agency thereof, nor any of their employees, makes any warranty, express or
implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any
information, apparatus, product, or process disclosed, or represents that its use would not infringe
privately owned rights. EPA hereby disclaims any liability for damages arising from the use of the
document, including, without limitation, direct, indirect or consequential damages including
personal injury, property loss, loss of revenue, loss of profit, loss of opportunity, or other loss.
Reference herein to any specific commercial product, process, or service by its trade name,
trademark, manufacturer, or otherwise does not necessarily constitute nor imply its endorsement,
recommendation, or favoring by the United States Government nor any agency thereof. The views
and opinions of authors expressed herein do not necessarily state or reflect those of the United
States Government nor any agency thereof.

c,EPA

United States Environmental Protection Agency
(4204M)

EPA 832-F-23-003
March 2024
vwwv.epa.gov/watersense
(866) WTR-SENS (987-7367)


-------