Modern Low-flow Toilets
Today's low flow toilets are much more effective and efficient, and their parts are more durable and replaceable. Using the chlorine tablets no longer destroys flappers and creates leaks. And if that does happen, finding the proper replacement flapper is much easier for the consumer. Furthermore, manufacturers have redesigned the hydraulics of tanks and bowls, improving water flow. Toilet manufacturers, in fact, now use sophisticated computer models to design the hydrodynamics of their toilets.
Low-flow toilets, also sometimes called ultra low-flow toilets (ULFTs), usually use one of two methods to clear waste: gravity or pressure-assisted. However, they all use 1.6 gallons (6 liters) of water or less per flush. Gravity toilets clear waste when you move the flapper and water is released, dropping from the tank and flushing through the bowl. Gravity drives the waste out of the bowl. Pressure-assisted toilets, by contrast, compress a pocket of air, which acts to energize the water that's released into the bowl with each flush. The air is compressed within a vessel inside the tank each time it refills. Pressure-assisted toilets are a little noisier than gravity-fed models and they usually are more expensive as well, starting at more than $150 versus $75 or more for gravity-fed models.
Since 1999, some toilets have been made available that use even less water per flush than the typical low-flow toilets. These are called high efficiency toilets (HETs) and utilize about 20 percent less water than the average low-flow toilets, or about 1.28 gallons (4.8 liters) per flush.
One type of high efficiency toilet is the dual flush. Push one button and solid waste disappears, and there's another for liquids. Solid waste is cleared with 1.6 gallons (6 liters) of water per flush, while urine is flushed away with only 0.8 gallons (3 liters).