Single-pass cooling can be eliminated by retrofitting the existing equipment with a
recirculating system or replacing with air-cooled equipment.
Potential savings can be estimated by measuring the existing cooling water dis-
charge with a gallon bucket and stopwatch and determining how often the cooling
water flows (e.g., how many hours per day and days per year). Many applications of
single-pass cooling water flow continuously. To estimate facility-specific water sav-
ings and payback, use the following information.
Current Water Use
To estimate the current water use of existing equipment cooled with single-pass
water, identify the following information and use Equation 6-1:
Flow rate of the discharge water from the equipment cooled with single-pass
Average daily use time. This will vary by facility and the type of equipment
cooled with single-pass water.
Days of facility operation per year.
Equation 6-1. Single-Pass Cooling Equipment Water Use (gallons per year)
= Single-Pass Cooling Equipment Flow Rate x Daily Use Time x Days of
Single-Pass Cooling Equipment Flow Rate (gallons per minute)
Daily Use Time (minutes per day)
Days of Facility Operation (days per year)
Replacing existing equipment cooled with single-pass water with an air-cooled
system or retrofitting with a recirculating cooling water system will entirely eliminate
discharge water use, as shown in Equation 6-2.