Summary: You can save your water use a lot if you save water in your bathroom.
1. Toilet is the biggest water consumer. Toilets made before 1993 need 8 gallons of water per flash, while modern ones need only 1.6 gallons of water.
2. You can also save water with a one-litter plastic bottle. Fill it up with some water and pebbles, and put it in the tanker of the toilet.
3. Plumbing leaks is another cause of water waste in bathroom. To check whether water leaks in the toilet, you can drop some water color in the toilet tanker and wait about 15 minutes and see if the water permeated into the toilet bowl. If the water is colored, it means the water leaks.
4. Next, you'd better replace the pre-1992 water heads to modern one because the water flow from the old ones is too fast and therefore can be wasted (maybe, if you are taking a shower).
5. Finally, use a cup when you brush your teeth instead of letting the water running. Plus, put trash in the trash bin rather than put it in the toilet and flush it away. Take a shower instead of bath.
~ Jason