Here's a simpler solution...
There’s a lot of waste of water going on these days, and most people do not realize it. In your day-to-day life you use way more water than one would assume. typical daily water waste comes out to about these figures..
Toilet flushing – 40%
Bath and shower – 32%
Laundry – 14%
Dishwashing – 6%
Cooking and drinking – 5%
Bathroom sink – 3%
So starting with you toilet would be a smart move. As it originally goes; you should put a brick into your toilet tank. That’s not such a good idea because over time the brick will corrode and chip tiny pieces into your plumbing. A better option would be to either secure the brick in plastic bag and make sure it’s air tight or fill up a plastic bottle with either pea gravel or water and let that sit in your tank. The average toilet uses 3 to 7 gallons with each flush. Placing a bottle in the tank would displace enough water to save a half to a full gallon each flush, that averages out to about 10 gallons a day.