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How to perform a water audit July 29th, 2014

A water audit is an accounting procedure that monitors where and how much water enters and leaves a water system. This allows the assessment of current usage, provides data needed to reduce water and revenue losses, and allows forecasts of future water needs. The principal purpose of a water audit is to accurately determine the amount of unaccounted for water (UAW) in a water system.

Below is a list of steps typically performed in a water audit.

Step 1: Water Use Inventory

It is important to develop an understanding of exactly how and where your facility uses water. To do this, an inventory of all water use points in the facility with flow rates must be developed.

Start with a walk through of the facility, identifying every point in which water is used. For items such as toilets and faucets, the inventory should include the item, its location and its flow rate. If the facility has low-flow fixtures or if flow restrictors have been installed, identify them on the inventory.

Do not overlook building mechanical systems. Mechanical systems account for approximately 25 percent of the total water use in an average building.

Step 2: Metering

Unfortunately, most facilities only have a single, master water meter. Readings from master meters will provide an indication of how a facility compares to other facilities, but it will not show where to look for areas where water use can be reduced, particularly if the facility is large or complex. Narrowing use down to possible areas where use can be reduced requires submetering.

Where and how submeters are installed depends to a great extent on the design of the water system serving the facility. Ideally, submeters would be installed on individual zones or floors of the facility. Equipment with large water use rates, such as cooling towers and process cooling equipment, would each have separate submeters.

Each meter should be read at least monthly. If there are suspicions that the readings for a particular meter are high, or if the readings for a meter suddenly increase, it will be necessary to read that meter more frequently; even on a daily or twice-daily basis. Meter readings taken while the facility is closed and processes are shut down is one way to narrow the search for leaks and losses. All meter readings should be logged and reviewed on a regular basis for unexplained changes.

Unaccounted for water must be calculated based on verified supply and consumption records, and various estimated usage figures (where necessary). A water audit is thus heavily dependent on accurate metering data, which is dependent on meter accuracy. Because of this, meter testing is critical to a successful water audit.

Water audits typically require an accounting of the following quantities:

  • Total water supply
  • Total water consumption (metered and un-metered)
  • Total unaccounted for water, water losses (apparent and real), leaks, etc.
  • Percentage of unaccounted for water
  • Metering statistics, such as brand and model, beginning and ending readings, etc.
  • Meter accuracy
  • Corrections for meter inaccuracy
  • Operational efficiency
  • Financial indicators (total revenue and costs, revenue lost, etc.)
  • Other, depending on individual state requirements

Step 3: Review Maintenance Practices

If water conservation has not been a priority in the past, chances are no one individual or group has the overall responsibility for conserving water. And as with many things in the world of facility management, if no one individual has responsibility for an item, then it is not a priority for anyone. As a result, specific water use related problems may have been seen by a number of people but not really noticed or acted upon.

Preventive maintenance programs have long been recognized as effective tools for improving system performance while reducing overall operating costs. With water use historically being an ignored or low priority item, chances are few preventive maintenance steps have been put in place to specifically address water use. How often are restrooms checked for faucets that don’t fully shut off or flush valves that leak or stick on? Does anyone ever test once-through cooling systems to determine that they are operating at the proper flow rate? How often are cooling towers and boilers checked to see that the make-up water systems are operating properly?

When maintenance issues occur within the facility, there is a system established whereby building occupants can report the problem. Does that process include water-use related issues? Do building occupants even know that they can and should report instances of excessive water use or waste?

Finally, what mechanism is in place to review water using items that are being purchased for use within the facility? For example, refrigeration systems that use once-through water cooling are less expensive and easier to install than closed loop systems. Closed loop systems however, have minimal water requirements. Is there an established procedure that reviews equipment purchases that addresses the issue of water use?

Step 4: Water Efficiency Plan

Once information has been gathered on how water is being used in the facility, an action plan can be established for reducing water use. The plan should identify who will take responsibility for implementation. It should make certain that individual has the authority and support needed to implement the plan.

The plan should set specific water use reduction goals for the facility. Those goals must be measurable, achievable and realistic. The plan must also identify a mechanism for periodically reviewing the success of the program in meeting those goals.

The water audit should have identified a number of areas in which water savings can be achieved. The water efficiency plan should set the priorities for implementation based on costs, benefits and available manpower.



Georgia Department of Natural Resources

Natural Resources Defense Council

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