Water Use Calculator Household Water Use Calculator for Hauled Water Enter the daily water usage per person and the number of people in your household: Connecticut: 35 gal./day1 - Phoenix Indoor: 55 gal./day2 - US Average: 83 gal./day1 - Idaho: 186 gal./day1 Daily Gallons per Person: Number of People in Household: Calculate Water Usage Results: Minimum Holding Tank Size Results: Water Use Calculator Data Sources: 1. Public Supply and Domestic Water Use in the United States, 2015, USGS2. Average Daily Water Use, 2016, City of Phoenix A Note on Daily Water Use: Daily water use numbers may vary greatly. This is because it depends largely on the water use habits of the members in your household. It also depends to a large extent on exterior irrigation and use of water efficient appliances and fixtures. Shop Home Services Keep In Touch Instagram Youtube X Logo Facebook-f