Toilets installed since 1994 use 1.6 gallons. In order to conserve water in your pre-1994 toilet you can install an early closing toilet flapper , which are available at participating local hardware stores. If you are considering installing a 1.6 gallon toilet, check out the 1.6 gallon toilet satisfaction survey . The jug can displace 10 gallons or more of water a day. We do not recommend you use a brick to displace the water.
Bricks eventually disintegrate in water and can jam plumbing lines.
Also be careful not to place the bottles where they will jam the flushing mechanism, and make sure you don't displace so much water that you have to double-flush. Double flushing wastes more water than you would save. A toilet with even a small leak can greatly increase your water bill. To check your toilet for leaks, put a few drops of food coloring in your toilet tank, wait 10 minutes. If, without flushing, the color begins to appear in the bowl, you have a leak, which should be repaired immediately.