It's rich in nitrogen and phosphorus, which gives you a nice fertilizer while you use the same water twice. Check the water taps in your home to see if they all have aerators or spray taps. An aerator mixes air with the water, which not only cuts the flow but reduces splashing. The spray tap is similar, but also can swing from side to side like a tiny showerhead. Select the appropriate water level for the size of your load of laundry.
Most washers now offer preset water levels for small, medium, and large loads.
Use full loads whenever possible. Please don't let the hose run. Instead, wet the car thoroughly, then turn off the hose while you swab the car with soapy water from a bucket. Use the hose again for a final rinse. A trigger nozzle is best because it turns off automatically.