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Water Efficiency at Southface
To flush, or not to flush…

By Beth Haynes

In most homes, toilets are the number one user of indoor water. Southface has installed a number of highly-efficient bathroom fixtures in the new Eco Office, as well as the Residential Resource Center. In the Eco Office, the first floor toilets will be Caroma Caravelle dual-flush toilets and Mansfield QuantumOne pressure assist toilets. The Caravelle offers two flushing options, a full flush which uses the standard 1.6 gallons per flush (gpf) and a half flush which uses only 0.8 gpf, which allows a significant reduction in wastewater when appropriate. Although these toilets are installed with traditional plumbing, the option to use the half flush will save 20,000 gallons per year. The QuantumOne uses a pressurized tank to flush with only 1 gpf, which represents a savings of 38% over a standard toilet.

The water catchement sytem in the Eco Office will be used to water the green roof and landscape and provide water for flushing toilets in the first level bathrooms and the composting toilets on the third level.
Design attributes go to Paul Morgan of RainHarvest Company and Greg Jeffers of McKinneys.

Fixtures on the building’s third floor, or office level, will serve 20 occupants. These include two Clivus Multrum foam-flush composting toilets. The foam-flush toilet looks and functions like a conventional toilet, however it uses much less water per flush and produces no sewage. Instead of relying solely on water to flush, the toilet uses a mixture of biocompatible soap and water to carry waste to the composting system below. Each flush uses 6 ounces of water, or only 3% of a conventional toilet, so that this system will save more than 20,500 gallons of water per year relative to a pair of toilets in a typical office building. While the Eco Office system is sized for an office, residential-sized units are available and operate with little maintenance and no odor.

In the Southface Residential Resource Center toilets by Kohler are low-flow, pressure assist models or Toto low-flow models, all designed to reduce water use. The Kohler toilets are 1.4 gpf

The Kohler "Steward" Waterless urinal is installed at the Southface resource center.

Urinals at Southface are by Sloan, Kohler and Clivus Multrum and are waterless. There is no water supply or flush valve, only a replaceable, biodegradable cartridge filled with a half liter of water and a biocompatible fluid sealant that acts as a vapor lock. The cartridge directs flow through the sealant, preventing odor and allowing all liquid waste to pass through. The cartridge is good for 7000 uses before replacement. Waterless urinals will save approximately 25,000 gallons of water per year compared to conventional fixtures. Several manufacturers have begun to market waterless and low-flow urinals to residential customers.

Sloan Solis low-flow, automatic faucets installed in all of the building’s lavatories are equipped with solar-powered electronic motion sensors that turn the faucets on and off. The water flow averages 0.5 gallons per minute compared to 2.5 gallons per minute of a conventional faucet. This low-flow feature will save 47,250 gallons of water per year.

In addition to these water conserving fixtures, all water used for flushing toilets inside the Eco Office will be collected from rainfall in rooftop and belowground cisterns. A 2,040-cubic-foot Atlantis® Water Management System RainTank cistern will store over 14,500 gallons of rainwater for flushing toilets and cooling mechanical heat exchangers in the Eco Office. The RainHarvest Company has installed similar cisterns in other commercial and residential properties in metro Atlanta.

The RainTank, manufactured from post-consumer plastic, is composed of individual panels, which snap together to create permeable cubes forming the skeleton of the underground cistern. Because the system is scalable, smaller systems can be installed for residential use. The cistern is wrapped with a 30 mil EPDM membrane to contain the rainwater. A Deep Root physical root barrier protects the cistern membrane from thirsty tree roots without the use of herbicides, and has a high post-consumer recycled content, as well. Above -ground cisterns and barrels that capture water from gutters and include attached hoses and overflow valves are other appropriate rainwater collection systems.

By installing any of these water saving or harvesting features, homeowners can save on their water bills and help safeguard our water resources for years to come.