13 Ecology Ablazingly

How Eco-friendly is a Dual-Flush Toilet

The American Institute for Architects reports a keen desire by homeowners to minimize utility costs, including increasing interest in dual-flush toilets. 

What is a Dual-flush toilet?

For those unfamiliar with the dual-flush system, there are separate buttons for liquid/paper and solid wastes. The liquid flush option typically uses slightly more than half the water of the solid waste flush, Sierra Club says. 

How Much Water Does A Dual-flush Toilet Save?

A dual-flush toilet will typically save .7 gallons, or 2.64979 liters, per flush.

How Dual-Flush Water Use Compared to Traditional Toilets

Eco Brooklyn, a contractor specializing in eco-design, calculated per person daily water use based on toilet type. Assuming the average person defecates once and urinates six times per day, Eco Brooklyn says, a dual-flush toilet uses 6.4 gallons of water per household member per day.

Since 1992, when the Energy Policy Act took effect, newly manufactured or installed toilets are allowed to use no more than 1.6 gallons of water per flush, according to the Environmental Protection Agency. 

A post-1992 single flush toilet would thus use 11.2 gallons of water per person per day. 

High-efficiency toilets are 20 percent more efficient than standard low-flow toilets, using 1.1 to 1.28 gallons per flush. Eco Brooklyn estimated 1 gallon per flush, resulting in 7 gallons daily water expenditure per household member.

Toilets manufactured before 1992 used up to 3.5 gallons per flush, EPA noted. Owners of pre-1992 toilets are using up to 24.5 gallons of water per household member per day for flushing.

Dual-Flush Water Savings Put in Perspective

Toilets are the primary source of home water consumption, accounting for about 30 percent of indoor water use, the EPA says.

Sierra Club estimates 7,000 gallons water savings per year for a family of four trading a post-1992 single flush system for a dual-flush. And it points out by buying a WaterSense-labeled toilet, a buyer is assured of performance as well as water savings. That’s a big issue for people who remember the early low-flush models which often didn’t live up to their promise, requiring multiple flushes to get the job done each time the toilet was used.

According to EPA, if every toilet were converted to a WaterSense model (a category that includes dual-flush and high-efficiency models) the nation would save some two billion gallons of water per day. On a yearly basis,that’s 640 billion gallons of wastewater prevented, more than two weeks flow over Niagara Falls.

Considering the average person flushes 140,000 times during his lifetime, installing a dual-flush toilet is one green initiative with a big impact.

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