Not a drop to waste

CSE: Do sensor-activated faucets really save water? J. PATRICK BANSE: Sensor faucets are more sanitary than handle-type faucets, and with preprogrammed “on” times, reduce the water use and possibility of leaving the faucet running longer than needed. Flow-control devices are the real water savers, as they limit the flow rate discharge of water to the user, which also minimizes spla...

06/01/2008


CSE : Do sensor-activated faucets really save water?

J. PATRICK BANSE : Sensor faucets are more sanitary than handle-type faucets, and with preprogrammed “on” times, reduce the water use and possibility of leaving the faucet running longer than needed. Flow-control devices are the real water savers, as they limit the flow rate discharge of water to the user, which also minimizes splashing and saves overall water use.

SHAWN MARTIN : Yes, in most cases. Many users leave water running while brushing teeth, shaving, and the like. Metered or sensor-operated faucets eliminate that waste. They also guard against situations where the water is accidently left running after the user departs. They have the added benefit of providing improved usability for individuals with disabilities.

ROB ZIMMERMAN : We don't know that sensor faucets save water. While the arguments others [like Martin, above] make are true, they are offset to an unknown extent by a higher usage rate. In other words, a higher percentage of people wash their hands in public restrooms if they don't have to touch the faucet. Some small studies suggest this more than offsets the water efficiency, but more work needs to be done.

CSE : What can existing commercial buildings do to cut back on water consumption when there are urban water problems?

MARTIN : There are several options. Conduct a water inventory to determine the flow rate of plumbing fixture fittings—any using more than EPAct 92 levels should be upgraded immediately; look for and repair any water leaks (faucets, toilet flappers, etc.); upgrade gravity flush water closets to WaterSense devices; install dual-flush commercial water closet flush valves; replace urinals with no-water or pint-flush models; check the aerators on faucets; consider changing faucets to metered or sensor-operated models; consult a plumber and see if a demand-driven recirculation system can be retrofitted to your system—they eliminate water dumped down the drain while waiting for hot water; replace commercial kitchen pre-rinse spray valves with low-flow models; and consider reducing the water pressure of your plumbing system.

ZIMMERMAN : [Responding to Martin] We [Kohler] also don't know whether dual-flush flushometers really save water. It's assumed that people use the short flush twice as often as the long flush, but that is based on residential studies of informed users. I haven't seen any field studies that show what the relative frequency of short to long flushes is in public settings.

CSE : Are there HVAC approaches to saving water?

BANSE : Collecting cooling coil condensate from air handlers and using it for cooling tower makeup is a good method. Make sure cooling tower blow-down meters are calibrated correctly and makeup water valves close off completely. Check that chilled and heating water systems remain as closed systems and are not leaking. Shutting down cooling systems during unoccupied times also is an option that limits or eliminates cooling tower evaporation and discharges to drain as long as there are no critical areas to keep in operation such as information technology systems.

CSE : What plumbing codes are prohibitive toward green technology? What plumbing codes are supportive toward green technology?

BANSE : I think all plumbing codes support green technology by requiring adherence to the energy code. This saves water through the use of flow restrictors in sinks and showers, low-flush water closets, and urinals. They certainly do not prohibit the use of less water. Codes allow collection and reuse of gray water as long as the piping systems are labeled properly. Some codes require separation of the black and gray water systems mainly due to the limited infrastructure and ability to treat wastewater. This encourages on site collection and reuse of gray water for irrigation and other nonpotable uses.

MARTIN : Some states and local jurisdictions have prohibitions or limitations on the use of no-water urinals. Some locales, such as the state of California, do not permit the use of PEX piping (although local jurisdictions are not precluded from permitting it). Model codes generally provide little support and guidance at this time for innovative piping systems beyond traditional trunk and branch systems. In addition, many plumbing supply lines are vastly oversized for the fixture fittings they supply. The water consumption of the fittings has dropped over the past two decades, but the pipe sizes have not dropped with them.

The model codes have each made significant commitments to improving their green attributes, and are following through. Gray water, piping systems and materials, no-water urinals, and sizing issues have all been addressed in new versions of codes to be released in 2009.

Plumbing Manufacturers Institute (PMI), like the U.S. Environmental Protection Agency's WaterSense program, endorses an approach that ensures that water-conserving devices not only save water, but also provide appropriate levels of performance and durability. Water is not conserved if users remove or tamper with devices out of frustration. PMI also advocates a holistic approach to water savings that takes into account the potential total water savings that can result from changes to devices, and what impacts will result from a change (both intended and unintended).

CSE : Would eliminating hot water from restroom sinks save significant water or energy, and is it allowable by code? Is hot water a sanitary/code issue or for comfort?

ZIMMERMAN : I definitely would not look to eliminating hot water from public lavatories. Fewer people will wash their hands, and the soap just doesn't clean as well with cold water. I have studies from the Centers for Disease Control and Prevention that indicate approximately 40% of common illness is spread by hand-to-mouth contact and could be greatly reduced by regular hand washing.

MARTIN : Possibly. Theoretically, if users do not need to wait for the hot water to arrive at the faucet, the water that would normally be dumped down the drain would be saved. However, for commercial installations where the hot water is supplied by a recirculation system, this is generally not an issue, because hot water is usually very close by.

As for code acceptance, most codes require that hot water be supplied to fittings and fixtures used for bathing, cleansing, washing, cooking, laundry, and the like (see 607.1 in the 2006 International Plumbing Code (IPC) or 10.15 in the 2006 National Standard Plumbing Code (NSPC)). A ready supply of hot water is considered vital for proper health and hygiene at lavatory faucets. Consider, for example, the signs hung in most restaurant restrooms declaring that state law requires restaurant workers to wash their hands before leaving the restroom.

BANSE : People will use the same amount of water to wash their hands regardless of which faucet is turned on. Providing hot water in toilet room sinks is a good engineering practice, as warm water is necessary for proper sanitation. Also, the use of tempered water in sensor faucets is desirable in cold-weather climates. Energy would definitely be saved (as well as first cost) if hot water were not provided at places where it was not required. I think it would depend more on the climate and desires of the owner.

CSE : What O&M issues are green buildings finding in the field from water-saving technology: gray water, rain harvest, no-flush urinals, etc.

BANSE : Keeping flush valves in calibration and working properly. Generally there are more components to check and maintain when gray water recycling and rainwater harvesting are used, such as level indicators and alarms, pumps and valve operation, cleaning of the holding tanks, and any discharge areas such as hoses or irrigation sprinklers. Also, keep the systems clean to avoid unwanted bacteria or related growth in the standing water. The no-water urinal fixtures are cleaned much the same as conventional fixtures except the liquid seal layer—whether floating on top or in a cartridge type—must be regularly checked to ensure the seal is being maintained and there are no escaping sewer gas or odors. Care needs to be taken that any cleaning agents used do not harm the liquid seal.

MARTIN : No-water urinals: Close adherence to manufacturer recommendations for cleaning of the urinal and replacement of the cartridges or sealant is essential to ensure that these devices continue to perform as designed.

Gray water/rainwater: The use of gray water and rainwater for indoor purposes such as flushing toilets has been promoted in many green building venues. While this has approach has much potential, codes and standards have not yet been put in place to ensure that the water does not adversely effect the internal components of toilets. There are no applicable standards in the United States defining the quality of any gray water and rainwater used for these purposes, so the effect of any given gray water source on components cannot be predicted. Before using any reclaimed water for toilet flushing, work with a professional to put in place a system to perform basic filtering and sanitization.

Rainwater: Harvesting systems should be cleaned and inspected regularly. Make sure that leaf and debris catchers are kept clean and that systems discarding the first flush of water are working properly. Also, clean the holding tank in accordance with manufacturers' instructions to keep water quality and function high.



Participants

J. Patrick Banse

Senior Mechanical EngineerSmith Seckman Reid Inc.Houston

Shawn Martin

Technical Director

Plumbing Manufacturers Institute

Rolling Meadows, Ill.

Rob Zimmerman

Senior Staff Engineer—Water Conservation Initiatives Kohler Co.

Kohler, Wis.

Ask the experts: no-water urinals

At CSE gives its readers and Web visitors the opportunity to pose questions directly to the panelists. Below is a question for June's topic, specifically about no-water urinals.

“ How are waste materials from no-water urinals disposed of?” —Tony [last name withheld], mechanical engineer, Atlanta

J. PATRICK BANSE : Trap seal liquids will generally wear out or degrade through prolonged use and will be “flushed out” with the liquid urine waste. Replacement of the floating liquid layer would be in accordance with the manufacturer's recommendations. The trap type seal is removed with a special tool and disposed of with normal solid waste products such as paper towels and related refuse.

SHAWN MARTIN : Cartridges are simply discarded with traditional waste. Some manufacturers provide bags in which to place the used cartridges before disposal. Many manufacturers encourage the draining of the cartridges and recycling of the plastic. The cartridges are not classified as hazardous waste. Another option is that most sealant liquids may be discarded in the municipal waste system.



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