High-efficiency toilets (HETs) have been defined by the plumbing industry and the Environmental Protection Agency (EPA) as those that use an average of 20% less water per flush than the industry standard of 1.6 gallons.

For a family of four, that can mean a savings of almost 9,000 gallons of water each year. That’s not only green, but it also makes sense, especially in an age where public water prices are on the rise and aquifers are being depleted.

The Partnership for Advancing Technology in Housing (PATH) highlights four styles of HETs on its list:

* The gravity-fed single flush toilet operates like a traditional toilet but can use as little as 1.1 gallons per flush.

* For households who want more than one option when flushing, the dual-flush toilet allows you to choose between one mega flush, which uses up to 1.6 gallons of water, or the more modest light flush, which rinses with only .8 gallon of water. These toilets average out to use about 1.2 gallons per flush over the course of a year.

* Next on the list is the pressure-assist toilet, which uses water line pressure or a small air compressor to force the 1.1 gallons of water through the bowl at a much higher rate of speed. These toilets can flush greater loads faster at a significantly lesser volume of sound.

* The final HET suggested by PATH is the power-assist toilet, which operates using a pump to force water down at a high velocity. Power-assist toilets require a 120-volt power source to operate the small, fractional-horsepower pump. Typical flush volumes are between 1 and 1.3 gallons per flush; dual-flush models are also available.