1
Save water from your taps. Turn the faucet/tap off while you are brushing your teeth, shaving, washing your hands, doing dishes, and so on. Turn the tap off when you shower, too. Get wet, then turn off the water while you soap up. Turn it back on for long enough to rinse. Look for a twist valve that installs behind your shower head to keep the water temperature where you set it while the water is off.
Catch the cold water that comes out of the faucet, tap, or shower while you are waiting for the hot water. Use it to water plants or pour into your toilet reservoir after flushing.
Water from a hot water tank may have more sediment or rust than water from the cold water tank, but is otherwise suitable for drinking. If you use a water filter, you can filter the saved water, and put it in bottles in the refrigerator for drinking water.