Out of all indoor household water use, toilets are the number one consumer.  More than 35% of household water use goes towards flushing the toilet.  There are some ways you can reduce the amount of water being flushed down the toilet though.  The low-flow, composting, and dual flush toilets are all options to help you conserve water.

LOW-FLOW TOILET

The average American uses 74 gallons (280 liters) of water per day, one-third of which splashes down a flushing toilet. Since 1992, U.S. law has mandated that new toilets sold in the United States be low-flow or low-flush, which means that they consume no more than 1.6 gallons (6 liters) per flush. Before that time, typical toilets sold in the United States used 3.5 to 7 gallons (13.24 to 26.5 liters) per flush.  There are toilets available which flush using an even lesser amount of water than the low-flow standard.  The new high efficiency toilet (HET) standard defines a HET fixture as one that flushes at 20 percent below the 1.6 gallons per flush maximum (that is, it has a maximum of 1.3 gallons per flush).Many homes still have the older models in them, so a low-flow toilet could installation would mean dramatic water and money savings.  If buying and installing a new toilet is too costly you can reduce your water used per flush by filling a water bottle with water and a few rocks and putting it in the toilet's tank.  A bottle in the tank will displace enough water to save half a gallon to a gallon each use, or up to about 10 gallons a day in a typical home.

COMPOSTING TOILET

A composting toilet may save more than 6,600 gallons (24,984 liters) of water per person a year.  The process works the same as the composting pile you may have for your kitchen scraps. Aerobic bacteria within the waste break it down with the help of air, heat and time. Someone does have to stir material regularly, and add materials such as sawdust or popcorn to keep those bacteria at work. The result is an earthy nutrient-filled organic matter known as humus. One person would produce approximately 80 pounds (36 kilograms) of humus a year.  Instead of flushing, the waste drops down a pipe to the composter, which is hidden from view with a trap door or screen.

For a self-contained composting toilet to work properly, ventilation is needed that can both keep the smell out of your bathroom while providing enough oxygen for the compost to break down. With some toilets, this is done with fans and a heater powered by electricity (some models do not require electricity).  The composter does have to be kept at a minimum temperature of 65 degrees Fahrenheit.

Health authorities vary widely in their acceptance of composting toilets.  For many areas it is only acceptable to use a composting toilet where sewage is not available.

DUAL FLUSH TOILET

The dual flush method has the advantage of intuitive flushing, where the operator can decide electively whether less or more water is needed to flush and press the appropriate button.  Most modern dual flush toilets use less than a gallon of water (3 liters, approximately) to flush liquid waste and around 1.6 gallons (6 liters) to flush solid waste.  Standard toilets use siphoning action, a method that employs a siphoning tube, to evacuate waste. A high volume of water entering the toilet bowl when the toilet's flushed fills the siphon tube and pulls the waste and water down the drain. When air enters the tube the siphoning action stops. Dual flush toilets employ a larger trapway (the hole at the bottom of the bowl) and a wash-down flushing design that pushes waste down the drain. Because there's no siphoning action involved, the system needs less water per flush, and the larger diameter trapway makes it easy for waste to exit the bowl. Combined with the savings from using only half-flushes for liquid waste, the dual flush toilet design can save up to 68 percent more water than a conventional low flow toilet.