There are several general approaches to the design of water-saving fixtures: low flow, dual-flush, waterless, and automatic sensor-type. Low-flow is the simplest and most common, including toilets, urinals, faucets and shower heads. Note that fixtures must be designed to operate correctly with less water – changing the valve on an older fixture will give unsatisfactory results.
Dual-flush toilets are gaining in popularity, where the user can choose either of two flush modes depending on the use of the toilet. Waterless urinals have been developed and used, but they require special maintenance (a special liquid to be added) and are not very popular. Manufacturers have responded with ultra-low flow urinals that use as little as .125 gallons per flush (this compares to 1 gallon per flush for a “standard” type.Automatic sensor-type faucets use very little water by limiting the flow rate as well as the time the fixture operates. Automatic operators are also used for toilets and urinals. In all cases, the sensors require electricity to operate. They may easily be wired to the building in new construction, or battery operated if added later. In the latter case, the batteries must be maintained. A new type of “self-generating” automatic valves have tiny water turbines inside that use the flow of the water to generate enough electricity for the next flush!
People generally do not like low-flow shower heads, but a range of “low-flow” is available, so a compromise can be reached between comfort and water savings. Low-flow shower heads and flow-restrictors on faucets are the simplest to install on existing plumbing – all it takes is a trip to the hardware store!