The first step in the quantification of water use is a water audit – a detailed examination of where and how much water enters the system, and where and how much water leaves the system. Water system audits facilitate the assessment of current water uses, provide data needed to reduce water and revenue losses, and forecast future demand. With this information, a facilities manager can target system improvements where conservation efforts are most needed.
A major objective of a water system audit is estimating and reducing unaccounted-for water use. Unaccounted-for water includes losses through leaks, inoperative system controls (such as blowoff valves and altitude-control valves), and water used from unmetered sources such as wells.
Step 1: Preparation and Information Gathering
Before beginning the actual water audit, collect pertinent information from company and utility records. Identify the people who are familiar with daily operations – particularly operations and maintenance supervisors and staff. Collect the following information:
• Building and location information, including physical size of the facilities, floor plans, plumbing schematics, and drawings;
• Operating schedules, including total number of employees and number of employees per shift;
• Location maps identifying each water supply meter that measures incoming (source) water, plus each water meter that records on-site use. (As commonly defined, a “submeter” measures water use for specific processes and individual buildings within a site.)
• Inventory of plumbing fixtures;
• Inventory of all water-using equipment with manufacturers’ flow rates;
• Outdoor water-use data, including irrigation systems, watering schedule, and water volume;
• Utility records (water and sewer) for the past two years;
• Records that show actual water use during the past two years (including meter and submeter readings, water wells, and water tank deliveries);
• Any prior water and energy audits;
• Anticipated water and sewer billing rates for the next two years (from utility).
Use the above referenced water records to determine the amount of water used to produce products. Graph the results to show monthly water use. For manufacturing sites, divide the amount of water used by the quantity of product manufactured to determine the gallons per ton or gallons per unit produced.
If your facility or organization has not attempted significant water conservation measures in the past, it may be beneficial to seek experienced outside assistance. Information and professional help may be available from other sites outside of your own company or organization, outside water and energy consultants, and local water, wastewater, and/or energy utilities.
Step 2: Conduct a Facility Survey
After the information in Step 1 has been collected, the next step is a physical survey of the facility.
Walk through the facility with production people and supervisors to understand how water is used in the various areas and production centers. Identify and list all equipment that uses water, including processing equipment, cooling towers, boilers, reverse osmosis filters, rinsing tanks, kitchen equipment, faucets, toilets, showerheads, etc.
Check the water-using equipment against your inventory information. Compare floor plans, plumbing drawings, and schematics with actual conditions. Note discrepancies so an accurate record of equipment can be created.
Record hours of operation for each piece of water-using process equipment. Whenever possible, verify schedules of use with operating personnel familiar with the building use and equipment. Note devices, equipment, and/or plumbing fixtures that use water for more than one operation. For example, some ice makers use water for making ice and for cooling. Calibrate all existing water meters to ensure accuracy.
Measure the amount of water used by each water-consuming fixture or piece of equipment. If permanent meters have not been installed, a temporary strap-on flow meter that uses ultrasonic waves to measure water flow can be used. In some cases, a bucket and a stopwatch can be used to measure the flow rate in gallons per minute. Compare your water-use measurements with the manufacturers’ listed and/or recommended flow rates. Note any discrepancies.
Ask for water conservation suggestions from employees who are familiar with each water-use process.
Measure water quality, too. Knowing the quality of water as it flows through a facility may point out areas where water discharge from one process can be rerouted for use in another process. Water quality considerations include: chemical make-up, pH level, conductivity, total dissolved solids in parts per million, waste content, and temperature.
Measure exterior water use, especially water used for irrigation. Obtain diagrams of all irrigation systems and inventory all sprinkler heads and water-delivery devices to determine flow rate.
Determine daily water usage for the major operating and production areas. Add these area totals to get total facility usage. Make sure that your total consumption figures match the total usage figures from your water utility, water well meters, and other water source records.
Step 3: Prepare an Audit Report
After the completion of the physical inspection of the facility, in which each water-use area was carefully examined and water-use data was recorded, it is time to collate the data into a final audit report. This report will provide the “baseline” by which your water conservation efforts will be measured.
Your report should include the following:
• An updated set of facility diagrams, blueprints, and water-flow charts;
• A current list of all water-using equipment with manufacturers’ recommended input/output flow rates and the actual flow rates recorded during your water audit;
• A current schedule of operation for all areas and equipment, including shift scheduling, number of employees per shift, production levels, etc.
• A month-by-month landscape irrigation watering schedule (landscape irrigation varies dramatically by month and by season);
• A water-flow chart that shows the movement of water from the time it enters the facility until it is discharged;
• Water-use figures (total facility, and broken out by operating areas and processes);
• Any additional water-use observations revealed by the walk-through audit and analysis;
• An evaluation of the total cost of water used by the entire facility (see Step 4).
Major discrepancies between your facility’s total water consumption figures and the sum of each water-using area may indicate underground leaks in your water delivery system. Further (more detailed) water measurement may be required to pinpoint the leak. Make sure your plan of action includes these leak-detection activities.
Step 4: Determine Total Water Cost
The line item on your utility bill is the most obvious expense associated with water use, but it is far from the total cost of water use. Some water utilities charge a fixed fee or an environmental surcharge in addition to the cost for actual water used. (Water quantity is typically billed in “units” that equal one hundred cubic feet, which is equal to 748 gallons.)
The cost of water can also vary. Some utilities charge different rates based upon the amount of water used. And water rates may vary seasonally. Summer rates may be higher than winter rates because water demand is greater during the summer months.
In addition to the utility cost, the total cost of water also includes the cost of:
• Heating;
• Cooling;
• Energy cost of pumping water from wells or to on-site locations;
• Pretreating, including filtering, purifying, and softening;
• Chemical treatment, including treating boiler feed and cooling tower water;
• Predisposal treatment;
• Disposal of hazardous aqueous substances;
• Sewer discharge, which can be based on the amount of water discharged, total dissolved solids, and other water-quality considerations.
Using the above information, add up the total annual cost for water and water processing. This total will be your current baseline for water cost. Calculate the cost for each unit of water consumed by dividing the total cost by the quantity of water used.
It may also be advantageous to calculate the cost of water used per production unit. To calculate that figure, divide the total cost of water use for a production run by the number of units produced during that run.
Be sure to note monthly differences in water costs, if any. Your “per unit” cost of water may be higher in the summer months, which could make water conservation efforts even more cost effective during these months.
October 2005 Render