Plumbing Retrofits: Spotlighting on Savings

  December 3, 2014

Maintenance and engineering managers have long recognized the benefits of upgrading their plumbing systems — reduced water use, lower energy costs, and decreased maintenance requirements. But top management in institutional and commercial facilities typically does not see upgrades the same way. Those making financial decisions generally make those decisions on the basis of financial impact.

Unless managers take the time to communicate the benefits of retrofit projects to top executives in these terms, chances are they will not receive the funding they need. Consider the challenges of quantifying the savings from plumbing and restroom retrofits. Domestic water use accounts for about 40 percent of the water use in most commercial and institutional buildings. Toilets, urinals, and lavatory sinks account for most domestic water use. Water closets and urinals purchased after 1992 have measured their flow rates in gallons per flush (gpf), typically 1.6 gpf.

For units with no flow-rate indicator, managers can assume they are pre-1992 models and use a flow rate of 3.5 gpf. The same goes for urinals. Record the number of each type of fixture and its flow rate for all lavatories in the facility.

For lavatory sinks, managers measure the flow rate using a stopwatch and a container of a known volume. Record the flow rate for each lavatory sink in the facility. Older units should have a flow rate of 2.5 gallons per minute (gpm) or higher, while newer ones should be in the range of 1.5 gpm or less.

The hardest part of quantifying domestic water use is estimating the number of people who use the restroom each day. Managers can make estimates by using a counter on the door to register the number of times each day a user opens the door or by counting the number of people who enter the restroom over a period of time. Neither method is exact, but it provides an indication of use. Managers can use a similar method to estimate the length of time each person uses the lavatory faucet.

Potential water savings will depend on the water use of the replacement fixtures. For water closets, newer-generation models use 1.28 gpf. High-efficiency urinals use as little as 0.125 gpf. New lavatory sink faucets have a flow rate of 0.5 gpm.

Managers can determine the potential for reductions in water use by multiplying the difference between flow rates of the existing and replacement components by the number of users per day and the number of days per year the restroom is in use. Multiplying this number by the cost of the water will provide the annual savings for the retrofit.

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