Toilets use a lot water to get the dirty work done. However, with the advent of low-flow toilets, we can save loads, making it more efficient and saving energy, too.
Low-flow toilets, also known as low-flush toilets, have been around for years. In 1992, the United States 
passed a law that all new toilets sold in the United States must be low-flow, meaning they can consume no more than 1.6 gallons per flush. Before that, the average toilet used 3.5 to 7 gallons per flush.
Types
Most low-flow toilets use a gravity or pressure-assisted technology to flush. Using these means substantial water savings, ranging from 1.9 to 7 gallons per flush. and, in turn, reducing the water bill by about $78 per year. All models use 1.6 gallons of water or less per flush. The difference between them is minimal in quality: gravity toilets clear waste when moving the flapper and water is released from the tank and flushing through the bowl. Pressure-assisted toilets compress a pocket of air, which moves the water released into the bowl with each flush. The air is replenished when it refills. Pressure-assisted toilets are a little noisier, and a little more expensive, but tend to last longer, too.
Another variation of these is the dual flush toilet. Buttons indicate whether you’re ridding the toilet of liquids or solids.Solid waste is cleared with 1.6 gallons of water per flush,whereas urine is flushed away with only 0.8 gallons.
How to Choose
When looking at the different toilets, you’ll want to keep a few things in mind:
- How well the toilet removes waste from the bowl?
- How noisy is it?
- How tall is it? Taller toilets, such as those designed for folks with disabilities, tend to clear waste better.
- How wide is it? Round bowls tend to flush better, too.
- Look for “high efficiency” on the label; these give you the most water and financial savings.
- Also look for the “WaterSense” label from the Environmental Protection Agency. These have been tested to make sure they use no more than 1.28 gallons per flush.
- Make sure it looks good and feels good; after all, you’ll be using it.
Using What You Have
Instead of purchasing a new toilet, you can also retrofit an older one to save water. The most common approach is to use a displacement device. These are placed inside the tank to displace water. Because they take up room, the tank doesn’t have to refill as much each time, and reduce the amount of water by about 4.2 gallons per toilet per day.
You can also use a displacement dam, a plastic dam wedged into the tank on both sides of the flush valve. These decrease water per flush by holding back a small amount of water, saving about 6 gallons of water per toilet per day.
Another option is the early-close flapper, a valve that shuts off the water flow to the bowl before the toilet tank is empty.
And when all else fails, when it’s yellow, let it mellow.