All toilets and most showerheads today meet the federal water-efficiency standards, but not all of these products perform satisfactorily. With toilets and showerheads, we include products that meet or exceed WaterSense standards, which includes performance requirements—although we go beyond WaterSense where there are issues not adequately addressed by the program. We also look for other products that conserve potable water, such as rainwater catchment and graywater recovery and reuse systems.
Eco-Flush is a urine-separating toilet made by the Swedish company Wostman Ecology and available by special order through the importer Ecovita. This toilet uses 0.05 gallons per flush (gpf) for urine and 1.2 gpf for solids. The urine flows through a separate pipe where it can be collected for use as fertilizer (urine contains most of the nitrogen and half the phosphorous contained in domestic wastewater). The plumbing should be sloped and regularly flushed with water and vinegar to prevent uric salts from building up. Solids are sent to sewer or septic system through traditional plumbing methods.
Toilet flushing accounts for up to 40% of water use in most residential buildings, making it the single largest water user. In turn, the opportunity for water savings from installing efficient toilets, and from toilet replacement, is significant. In addition to improvements to the traditional gravity system, pressure- and vacuum-assisted flushing systems have been developed that offer superior performance, albeit often with some increase in flushing noise.
Flush volume – no more than 1.28 gallons per flush
Flushing performance – minimum 350 grams per the Maximum Performance (MaP) test
Fill valve – pilot valve type or equivalent performance
Tank capacity – maximum holding volumes for tanks (with quantities determined by tank and flush type)
Product marking – labeling and installation instructions that uphold the above criteria
Dual-flush toilets comply with WaterSense by making two flushes available: one for solid wastes and a lower-volume flush for liquids and paper. For dual-flush toilets, WaterSense factors water savings by averaging the high and low volume flush levels. Two reduced flushes and one full flush cannot average more than 1.28 gallons per flush.
GreenSpec users, however, should be aware of the limitations of the WaterSense criteria. MaP Test results many times higher than the 350 g minimum may come at the expense of other bowl-clearing aspects of performance, such as:
Floating or dissolved media clearance
Back wall clearance
To the extent possible, GreenSpec considers these other aspects of performance qualitatively (as GreenSpec users should as well) because no other publicly available standards are available.
GreenSpec lists toilets that are WaterSense listed and can flush 500 grams per MaP testing. Toilets that are included without WaterSense labeling are extremely low-water (ultra-efficient) use or have other unique green features.
Composting toilets convert human waste into nutrient-rich fertilizer for nonfood plants, rather than mixing the waste with potable water and flushing it down the drain.
Advantages of composting toilets include dramatic reductions in water use, reduced groundwater pollution or sewage-treatment impacts, resilience (ability to operate during water shortages), and recycling of nutrients.
Some composting chambers can be used with microflush and foam-flush toilets, though most use no water. Proper sizing is critical for effective composting; a model with undersized capacity won’t function appropriately. If composting toilets are used, graywater treatment and disposal still need to be addressed.
WEc1: Water Use Reduction
WEc2: Innovative Wastewater Technologies
WEc3: Water Use Reduction
WEc3.1-3.2: Water Use Reduction
WEp1: Water Use Reduction—20% Reduction
WEp1: Minimum Indoor Plumbing Fixture and Fitting Efficiency
WEp1: Water Use Reduction
Ratings and Commentary