# Page 240 - WaterSense at Work

7-22
October 2012
Water Savings
On average, a vacuum retrofit or replacement that modifies the ejector can reduce
vacuum water use by at least 50 percent.
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To calculate the water savings that can be
achieved from this type of modification, identify the current water use of the equip-
ment as calculated using Equation 7-6 and use Equation 7-7.
Equation 7-7. Water Savings From Steam Sterilizer Vacuum Retrofit or
Replacement With Additional Ejector (gallons per year)
= Current Steam Sterilizer VacuumWater Use x Savings (0.5)
Where:
••
Current Steam Sterilizer VacuumWater Use (gallons per year)
••
Savings (percent)
Payback
To calculate the simple payback from the water savings associated with retrofit-
ting or replacing an existing steam sterilizer vacuum, consider the equipment and
installation cost of the retrofit or replacement, the water savings as calculated using
­
Equation 7-7, and the facility-specific cost of water and wastewater. An ejector modi-
fication vacuum retrofit typically could cost approximately \$17,200.
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By retrofitting an existing steam sterilizer vacuum with an additional ejector, facilities
should also consider the potential energy impact. The pump and other equipment
included with the retrofit or replacement can use additional energy. The energy use
can affect the payback time and cost-effectiveness.
Steam Sterilizer Replacement With Liquid-Ring Vacuum Pump (Vacuum
Water Use)
When replacing a steam sterilizer, facilities can also select models that have an elec-
tric liquid-ring vacuum pump instead of a high-velocity ejector. Liquid-ring vacuum
pumps can reduce vacuum water use by 75 percent compared to the water used
through the vacuum generation on a conventional steam sterilizer.
Current Water Use
To estimate the water use of an existing steam sterilizer’s vacuum, use Equation 7-6.
Water Savings
Purchasing a new steam sterilizer with an electric liquid-ring vacuum pump can re-
duce vacuum water use by approximately 75 percent.
39
To calculate the water savings
7.4
Steam Sterilizers
37
Ibid
.
Page 27.
38
Ibid
.
39
Ibid
.
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