Office Building Introduction

Office facilities are a great opportunity for water conservation and water use efficiency.  There are numerous retrofits available for the water-using equipment and fixtures within the typical office building complex.  Developing a water use profile often leads to short payback periods for retrofits.  Generally speaking, office facilities are usually a large portion of a utility’s commercial sector, and the strategies employed are only slightly more complicated than the residential sector.

The greatest impediment to achieving meaningful water savings in this sector is the common disconnect between the person that pays the water bills, the building owner, the tenants, the building manager or engineer, and the various third party contractors that maintain the facility and equipment.  In multi-use or multi-tenant properties, water saving potential is frequently enormous, but successful implementation of changes always requires a cooperative effort from everyone involved.  The common water efficiency opportunities are as follows.


Water savings can be achieved by replacing older model toilets using 3.5 gpf (13 Lpf) or greater with new ULFTs (1.6 gpf -6 Lpf), HETs (1.28 gpf - 4.8 Lpf), including dual-flush HETs using 1.6 gpf (6.1 LPF) for the full flush and no more than 1.1 gpf (4.0 Lpf) for the reduced flush (liquid waste).  The frequency of toilet flushes per toilet is often greater in offices than homes, although the frequency is highly variable from facility to facility.  It is reasonable to assume an average of 2 to 4 flushes per person per 8 hour shift.  Depending on the type of business conducted, transients (visitors and customers) might also incur additional flushing activity.  When conducting benefit/cost analyses, it is important to separate the calculations for women’s toilets versus men’s toilets for two reasons: (1) the ratio of mens room toilets per male worker is usually different than the ratio of womens room toilets per female worker; (2) men will most often use urinals (when available) rather than toilets.  While it is reasonable to use average toilet usage estimates for program planning, performing toilet retrofit projections of water use on individual office facilities requires calculations based on unique site data.  A sample calculation might be:

Data:    260 work days per year

300 male workers, 200 female workers

            10 male toilets, 15 urinals

            25 female toilets

            Male Toilet Flush Quantities:

                        260 days X 300 males X 0.5 toilet flushes/day = 39,000 toilet flushes/year

39,000 flushes / 10 toilets = 3,900 flushes/year/male toilet

Male Urinal Flush Quantities:

            260 days X 300 males X 2.5 urinal flushes/day = 195,000 urinal flushes/year

            195,000 flushes / 15 urinals = 13,000 urinal flushes/year/urinal

Female Toilet Flush Quantities:

                        260 days X 200 females X 3 toilet flushes/day = 156,000 toilet flushes/year

            156,000 flushes / 25 toilets = 6,240 flushes/year/female toilet

Conclusion: This example shows replacing female toilets will garner nearly 35% more water savings compared to male toilets.

The dominate type of toilet installed in office buildings is the flushometer valve/bowl combination and the pressure-assist, though gravity-fed, tank-type toilets are found occasionally.  For example, when retrofitting from a 3.5 gpf (13 Lpf) flushometer fixture to an HET flushing at 1.2 gpf (4.5 Lpf), both the bowl and the flush valve of the flushometer valve/bowl combination must be replaced to assure water savings and adequate flushing performance.   The cost to replace a flushometer type toilet usually ranges from $250 to $400, depending on the type of bowl and valve chosen.  Wall-mounted, back-outlet flushometer valve/bowl combinations are the most commonly found in new buildings, while floor mounted fixtures are more common in older buildings.

As with all toilets in the commercial sector, there are a few extra items to consider when choosing products:

  • Building maintenance staff must be trained to only use the proper parts when servicing the flush valves, or all or a significant portion of the expected water savings will likely be negated.  Unfortunately, 3.5 gpf (13 Lpf) parts often fit the new 1.6 gpf (6.0 Lpf) flush valves.
  • There are now hundreds of models of HETs available (Up to 1.28 gpf - 4.8 Lpf) including single-flush and dual-flush. While there are many gravity type toilets suitable for light commercial applications, flushometer valve/bowl combinations or pressure-assist models are preferred in most commercial buildings.
  • Sensor-activated flush mechanisms often result in more frequent toilet flushing than manual flush valves.  There is no evidence the sensor-activated valves save water.
  • If installing dual-flush toilets, it is wise to post instructions for the toilet users, most of whom will be unfamiliar with the dual-flush technology and its operation,
  • Disposable seat covers and paper towels are the most common causes of clogged commercial toilets.  Consider alternate methods of hygiene (sanitizers, continuous roll seat cover dispensers, hot air dryers, etc.), or select new toilets models that exceed 500 grams (1.1 pounds) in Maximum Performance (MaP) Testing. 
  • Flushing performance is very important for success.  Refer to the MaP testing report before selecting new toilets.
  • Piston-type flush valves (as opposed to diaphragm-type)  more accurately meter the volume of water per flush and tend to have less maintenance issues.


The water-saving benefit of replacing urinals is highly dependant on frequency of use and the type of replacement proposed.  Frequency of use is determined by calculating the quantity of male 8-hour shifts, the average urinal flush per person per 8-hour shift (usually 2 to 4), and the quantity of urinals.  Similar to toilets, visitors to the facility might increase the total number of urinal flushes on a given day.

There are many options now for urinal replacements; from simply replacing the flush valve to reduce flush volume, all the way to replacing the entire fixture with a high-efficiency urinal (HEU). An HEU includes both flushing (maximum flush volume of 0.5 gpf (1.9 Lpf) and non-water using urinals.  There is significant variance in the short-term and long-term costs of each type and the long-term benefits. In many cases, marginal water savings can be achieved by simply retrofitting the urinal flush valve to a lower gpf diaphragm on flushometer valve urinals, though some older urinals will not properly function at these reduced flows.   Unfortunately, this type of valve-only retrofit can be easily and mistakenly reverted back to the higher flush volume during routine maintenance.  Much consideration is needed to determine the best retrofit or replacement for any given restroom.  To assure water savings are sustained over time, the best strategy is to replace the entire urinal and flush valve with an HEU (e.g., 0.125 gpf or 0.25 gpf (0.5 Lpf or 0.95 Lpf) model. 

The U.S. EPA has released a WaterSense specification for flushing urinals and will soon be allowing manufacturers to place the WaterSense label on these fixtures. Facilities managers, building engineers, and other decision-makers should consult the list of WaterSense urinals before making a product choice.

As with all urinals in the non-residential sector, there are a few extras items to consider:

  • Building maintenance staff must be trained to only use the proper parts when servicing the flush valves or all water savings will be reduced or negated altogether.  Unfortunately, 3.5 gpf (13 Lpf) parts often fit the new 1.0 gpf (3.8 Lpf) flush valves.
  • Sensor-activated flush mechanisms often result in more frequent urinal flushing than manual flush valves due to what is known as “phantom flushes”.  There is no evidence the sensor-activated flush valves save water.
  • Non-water urinals are considered compliant by most, but not all, plumbing code authorities.  The Uniform Plumbing Code and the International Plumbing code allow the urinals, but some local jurisdictions have not yet approved the devices.  It is wise to contact the local jurisdiction before installing non-water urinals. Furthermore, the maintenance costs associated with non-water urinals usually exceed those of flushing urinals.  It is essential that the building engineer or facility manager perform a fully life cycle cost analysis of the non-water urinal and comparing it with a similar analysis of a flushing urinal BEFORE making a purchase decision.

Lavatory Faucets

Flow rates for wash basin faucets in lavatories can reasonably be reduced to 0.5 gpm (1.9 Lpm) or lower.   (The current national standard and the major model plumbing codes in the U.S. call for a maximum flow rate in non-residential lavatory faucet installations of 0.5-gpm (1. 9 Lpm).)  Projected savings from retrofit (aerator replacement or replacement of the entire faucet assembly) are usually based on usage frequencies similar to toilet and urinal use.  Flow durations are often estimated to be 5 to 30 seconds per use.  Retrofitting aerators on the faucets is the most common and least expensive strategy.   The water savings are small when compared to replacing toilets, but the cost of retrofit is minor, usually less than $1.00 per faucet.

Some lavatories are fitted with mechanical metering valves (automatically shut-off after a preset time span) or negative shut-off valves (user must continue to exert pressure on valve handle to maintain water flow).   These types of valves are required to save water and deter flooding the lavatories.   The metering valves are often adjustable for the duration of the flow.  The flow should not exceed 5 seconds per activation.

There is no scientific evidence that sensor-activated faucets save water.  To the contrary, recent studies have provided valid evidence that sensor faucets use much greater water than manually activated valves.   It is important to note that the growth of the "touchless restroom" has been in large part to the concern for hygiene since fixtures do not need to be touched with the hand.   The studies shows that on the average,  users open the faucet to a flow rate of some 1.0 to 1.5 gallons per minute.  By contrast, sensor faucets open the valve all the way to the maximum flow setting.  If a 2.2 gpm aerator is on the faucet , the flow will be 2.2 gallons per minute, but if a 0.5 gpm aerator is used, the flow will be only 0.5 gpm.


Office buildings might also provide opportunities to conserve water used to irrigate surrounding landscape, especially office complexes with extensive common area landscaping.   These landscapes are notoriously over watered because: (1) the leasing agents demand a lush landscape to attract potential renters; (2) the landscape is maintained by a contractor that does not pay the water fees; and, (3) the landscape is usually irregularly shaped without zone separation between turf and lower water use plants.   The greatest difficulty in achieving irrigation savings is coercing the building owner to make the landscape maintenance contractor responsible for water use and waste.

Cooling Towers

Cooling towers can significantly increase the use of water in an office building.  Most large buildings (more than 10,000 square feet (1,000 square meters ) employ the use of a cooling tower in the HVAC system to cool the building.  Cooling towers use the cooling effect of evaporating water to remove heat from water circulating through the HVAC chillers.  Cooling towers can account for between 15 percent and 50 percent of an office building’s water use, depending on the climate in its location. There are numerous ways for the system to waste water when the system is not properly maintained.   In fact, depending on the climate zone and the cooling system, the water waste can be greater than that used by all the sanitary fixtures combined!  Appropriate retrofits usually require a conductivity controller be installed and properly maintained to achieve a first level water use efficiency.  Conductivity controller retrofits usually cost less than $1,500 per cooling tower, and can save more than $800 per year for a typical office building.

Cooling tower retrofits and maintenance should be part of every water conservation program targeting office buildings.  There are ample technologies available to greatly improve the water efficiencies of most cooling tower systems.  Technology provides the tools for water savings, but does not guarantee water efficiency.  Controller installations and retrofits must be part of an overall customer maintenance and education program to be effective.

Reclaimed Water

Where the local wastewater treatment agency provides reclaimed water (wastewater treated to drinking water standards, though deemed non-potable), office buildings provide an opportunity to supplant potable water use with reclaimed water use.   Landscape irrigation is the most obvious opportunity to use this water.  Reclaimed water can also be used to supply water to toilets and urinals.  Depending on the water quality requirements, many cooling towers can also use reclaimed water rather than potable water as their primary source.

In all applications, the reclaimed water must be strictly separated from potable water sources and end-uses.  This requires a clear separation of pipes supplying water to the end use (irrigation system, toilets, urinals, cooling tower, etc) from those pipes supplying potable water to faucets, drinking fountains, etc.  In large projects, irrigation systems are usually supplied through separate meters; thus, this is the most common application for reclaimed water use. 

The water supply plumbing for toilets and urinals is often interconnected with faucets and drinking water fountains; requiring extensive plumbing system retrofits if reclaimed water is to be substituted for flushing.  Retrofitting a pre-existing plumbing system inside an office building is usually too costly to justify the use of reclaimed water to flush sanitary fixtures. 

When constructing a new office building, the cost to separate the water supply plumbing for sanitary fixtures is marginal.  Some water agencies are now requiring new commercial buildings to be dual plumbed so reclaimed water can be used to flush sanitary fixtures, even if reclaimed water is not immediately available.  Commercial property developers report this has added less than 15% to the total cost of the plumbing system. 

Alternate On-Site Sources of Water

Alternate sources of water collected on the site of the office building can significantly reduce the use of potable water for non-potable purposes. These alternate sources include but are not limited to: 

  • Rainwater
  • Stormwater
  • Graywater
  • Air-conditioning condensate
  • Fountain drainwater
  • On-site wastewater treatment
  • Pool drain and backwash water
  • Cooling tower blowdown
  • Reverse osmosis reject water

Non-potable uses of water from these alternate sources can include:

  • Cooling tower makeup
  • Landscape irrigation
  • Pollution control
  • Toilet and urinal flushing
  • Swimming pool, fountain, and pond makeup
  • Laundry operation
  • Any other use not requiring potable water

Quality, quantity and time of generation and need all need to be matched and treatment provided, where necessary, to meet the requirements of the end use, comply with health codes, and satisfy environmental considerations.