Customer satisfaction surveys show that today's low-flow and high efficiency toilets perform far better than the water-wasters (3.5 gallons and more) they've replaced. But there are differences among toilets, and the following factors influence how well a new toilet performs.

• Waste removal: how well the toilet removes waste from the bowl


• Noise: Noise doesn't usually affect clearance of waste from the bowl, but it can affect your satisfaction with a toilet.


• Design: Design can affect the performance of a toilet, John Koeller of the Alliance for Water Efficiency told HowStuffWorks. Bowls that are compliant with the Americans with Disabilities Act -- about an inch and a half taller than a standard toilet -- tend to clear waste better than standard height toilets. The reason? The water has more distance to fall, giving it more of an opportunity to clear waste. Round bowls also tend to be better at flush performance than elongated bowls because they're smaller, which means the released water can be more efficient at removing waste.

What should you look for when buying a low-flow toilet to get the most out of your investment?

• Look for models that are labeled as high efficiency toilets. These toilets will give you the most water and financial savings. And, in some locations in the United States, sizable rebates are available to water utility customers for these toilets.


• Make sure you get a toilet with a "WaterSense" label from the Environmental Protection Agency. These toilets have been tested by independent laboratories to make sure they use no more than 1.28 gallons (4.8 liters) per flush (and are thus high efficiency toilets) and can also clear waste effectively, according to the MaP testing protocol.


• Realize that expensive toilets are not necessarily better toilets. Paying more for a toilet won't get you better waste clearance from the bowl, but it may give you more pleasing aesthetics in terms of color, bowl shape or whether the toilet is a one-piece or two-piece model.


• Choose a pleasing design. Toilets come in varying designs, including those that are ADA height, and bowls with round or elongated design. Toilets also have different seat shapes. Think about what you want in terms of toilet aesthetics, and if you want an elongated design, be sure to measure your bathroom to make sure there's enough room.

The United States is not the only country that has discovered the advantages of low-flow toilets. Australia mandates that all new toilets sold be dual flush. Sweden has restricted new toilets to low-flow (1.6 gallons/6 liters per flush) for many years. However, Canada still allows older style toilets (using 3.5 gallons/13.2 liters of water or more per flush) to be sold. But Ontario requires that all new construction have low-flow toilets.

In the United States, city and state governments are moving to even tougher legislation on toilets. In California, a bill signed into law in 2007 requires that all toilets sold and installed in California after Jan. 1, 2014, be high efficiency toilets. Other states like Georgia and Texas and cities like New York have considered similar requirements. In DeKalb Country, Ga., near Atlanta, legislation requires low-flow toilets in all older homes sold on the real estate market. And many consumer advocates say that even more restrictions on toilets will eventually be written into federal law, requiring that all new toilets be high efficiency models.

To make it easier to buy a low-flow toilet, many utilities and cities are offering significant rebates and vouchers to those who buy them. The Metropolitan Water District of Southern California, for instance, offers rebates valued at up to $165 for those who buy a high efficiency toilet. In Pasadena, Calif., Pasadena Water and Power offers a $265 rebate to owners of commercial and multi-family dwellings who purchase dual flush high efficiency toilets. DeKalb County in Georgia pays $50 to $100 per toilet to homeowners who buy low-flow toilets, up to three toilets per home.

If you'd like to save water, but don't want to invest in a low-flow toilet, there are a few ways to retrofit a toilet so that it uses less water.

The most common approach is to use a household displacement device. These devices are placed inside the tank in a place where they won't affect flushing and do just what you'd think -- displace water. Because they take up room inside the tank, the tank doesn't have to fill up with as much water each time you flush. Some typical displacement devices include plastic bottles (for example milk bottles) or bags filled with water, or bricks.

Displacement devices can reduce the amount of water a toilet uses by about 4.2 gallons (15.8 liters) per toilet per day, reducing water usage by about 13 percent, according to the Sustainability of Semi-arid Hydrology and Riparian Areas (SAHRA) research institute.

But there are cautions for using displacement devices, and they're not recommended as a long-term solution. Bricks can deteriorate and cause damage to the flushing mechanism, unless they're wrapped in plastic wrap or a small garbage bag. Plastic bottles or bags usually need to be weighted (with pebbles, for example) to make sure they're stable.

Another way to retrofit a toilet is to use a displacement dam. These are plastic dams that are wedged into the tank on both sides of the flush valve. They decrease the amount of water per flush by holding back a small amount of water. The water held back by the dams is not used, thus decreasing the amount of water used per flush. Displacement dams save about 6 gallons of water per toilet per day, according to SAHRA. One advantage they have over homemade displacement devices is that they're less likely to move around in the tank and disrupt the flushing mechanism.

Yet toilet dams and other displacement devices deteriorate over time and should not be employed as a long-term solution, according to Koeller. They definitely affect the flush performance of a toilet, which can lead to more frequent double flushing. When this happens, the expected water savings may never materialize.

Another retrofit device is the early-close flapper. An early-close flapper valve shuts off the water flow to the bowl before the toilet tank is empty. They're adjustable so that a homeowner can ideally find a level at which they can save water and still have the toilet bowl cleaned with each flush.

Still, all retrofit devices generally affect how well a toilet functions, and retrofitted toilets simply don't work as well as new low-flow and high efficiency toilets in clearing waste, according to Koeller. And since low-flow toilets with excellent performance are available for less than $100, it's hard to find reasons to choose retrofitting instead, he adds.