Property managers are becoming increasingly aware of the benefits of water efficiency for savings and sustainability.

Water efficiency opportunities in commercial buildings are typically identified by conducting a water usage audit. By examining the existing water usage profile of a building, an auditor can identify water loss within a facility, and determine the equipment changes and process optimizations that will achieve cost-effective water use reductions.

Opportunities within an individual building vary. The tenant profile is a key factor.

Efficiency measures include:

• Eliminating “single-pass” once-through cooling systems and substituting multiple cycle units.
• Installing water efficient toilets and urinals. Domestic use such as toilet flushing accounts for a large portion of an office tower’s water usage. The average water savings with water efficient fixtures is more than 200 litres for every 10 occupants per day.
• Installing water efficient faucet aerators in lunchrooms and bathrooms. Even a small measure like this can save between 1.9 and 3.8 litres (0.5 to 1 gallon) of water per minute of use.

For properties with a more diverse tenant profile such as mixed commercial use, including restaurants, dental clinics or other businesses that typically consume a higher than average volume of water, additional water efficiency measures specific to the activities of each business may also be considered. For example, restaurants that use a water efficient pre-rinse spray nozzle stand can save more than 1,200 litres of water per day.

The decision to implement a water saving project is usually dependent on the balance between implementation costs and the actual savings resulting from each measure implemented.

Water efficiency best practices
In the City of Toronto, water audits conducted at commercial buildings have identified conventional cooling towers as typically consuming the largest volume of water.

Since many commercial towers within Toronto are situated in close proximity to Lake Ontario, some building owners are presented with the unique opportunity to replace conventional cooling towers with the deep lake water cooling system. Utilizing the cold water drawn from the bottom of Lake Ontario as a source of cooling eliminates the need for water to be supplied to once-through cooling towers. Moreover, as energy is no longer required to chill the domestic water being used in the tower, building owners are seeing a reduction in their energy costs. To date, replacing conventional cooling towers with the deep lake system has contributed to saving 400,000 cubic metres annually in Toronto.

For buildings that do not have the option of replacing cooling towers with a deep lake system, conversion to closed-loop cooling towers from single-pass systems is a viable option. In contrast to a single-pass system (in which water passes just once through the system before discharging into the sewer), a closed-loop cooling tower recycles and re-cools the used water, providing an opportunity to reduce water consumption by a significant amount. Independent cooling units for computer rooms can be incorporated into the building chilled water system to further enhance water use efficiency, with the potential to save up to 5,000 cubic metres of water annually.

Conventional cooling towers can also be made more water efficient with the installation of a controller. Controllers monitor water purity and regulate the amount of fresh water that must be added to the system, decreasing the amount of water required to run the system. A controller can reduce water use by 2,700 to 5,100 cubic metres annually.

By replacing water-cooled air conditioning units and freezers with air-cooled units, building owners can save 1,600 to 10,000 cubic metres of water per unit annually.

Payback and incentives
Payback periods on water-saving measures vary. To maximize the cost effectiveness of water efficiency projects, building owners often select projects with the shortest payback period for early implementation.

Payback for an individual computer room cooling unit incorporated into the building chilled water system is 1.5 to 2.5 years, and a closed-loop water cooling tower with a controller is two to three years.

Building owners can attain two to three-year savings from the resultant lower water bills, which can fund other water efficiency measures with a longer payback period.

Local municipalities may offer incentives to help commercial properties become water efficient. The City of Toronto offers rebates of up to $150 for changing to water efficient toilets and urinals.

Capacity buyback programs (the costs of an initial water audit are paid by the municipality) and per litre of water saved programs are becoming popular.

Renee Chu is a water efficiency coordinator at the City of Toronto.