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Sustainability 103: dual-flush toilets can save the future!

Frame in that dual-flush toilet now!
Frame in that dual-flush toilet now!
Photo by Rick Zimmerman

Earth is awash in water. More than 3/4ths of the planet is covered in water, much of it to considerable depth. And let’s not forget all of the water that is currently trapped in ice- and snow-pack all across the globe. Or the water constantly swirling about and falling upon the surface as the result of our ever-changing weather.

Yet Earth is also water-scarce, at least as far as we humans are concerned. For we can survive only on fresh water. But the vast majority of the planetary water supply is saltwater. Fresh water constitutes a mere 0.20% or less of the worldwide total water supply. If we measure potable fresh water — that is, fresh water that’s actually fit for human consumption — we are now down to around 0.06% of the worldwide reserve of water.

Perhaps most sobering of all is the fact that all human consumption of water throughout history — for drinking, growing crops, bathing, carrying our waste, etc. — has made use of that same 0.06%, over and over and over again, endlessly recycled and repurified. Thus, each day, roughly 1/6th of the entire global population must spend considerable time and energy seeking out good drinking water. Despite that struggle, many succumb to illness and disease due to poor water quality. A recent United Nations study has indicated that investments in water quality improvement can reap an eight-fold payback in increased human productivity and averted health care costs.

Across America, 36 states currently and regularly experience local, regional or state-wide water shortages. We too often use water unwisely or inefficiently, and pollution — whether from agricultural runoff or industry — and rapid population growth and development can exacerbate a region’s water stresses.

Of the potable water used throughout most American cities, more than 80% is consumed in buildings. Clearly, we can go a long way toward greater water conservation, if we simply focus on improvements in consumption, use, waste and recycling of water within buildings. Thus, through effective design and construction, architects, builders and landlords can serve key roles in sustainability of water resources.

When it comes to residential potable water use, almost 60% of all water travels through valved appliances, like faucets, showers and toilets. The improvement of valve designs, shutoffs, and sprays, and the development of low-flow or dual-flow controls can greatly affect water use.

There are many agencies and advocacy groups aiding in the conservation of our water resources. The US EPA has developed standards for fixture water flows through its WaterSense program, and these have been endorsed and improved upon by such entities as the Alliance for Water Efficiency, the ASHRAE Green Guide and USGBC’s LEED standards. As such programs and standards become more widespread, we will see water consumption per capita trending downward.

Toilets have always stood out as a prime candidate for improvements, both since we all use them, and since they consume roughly a third of all potable water use in residences. Whereas some toilets may be pressure-assisted by forced air, or simply gravity-flush and thus reliant on gravity and the weight of the flushing water, many newer high-efficiency toilets are dual-flush. These employ a flush of up to 1.6 gallons for solid waste, and 1.0 gallons for liquid waste. The water savings achieved by switching to dual-flush toilets can be as much as 12,000 gallons per residence per year.