Optimum tank size for large rainwater harvesting system

Abstract

AbstractThe efficiency of rainwater tank systems depends on tank size, local climate, and potable water demand. This study investigates optimum tank size to maximize water saving potential in semi‐arid Southern California using a simple daily water balance model. The model evaluates the performance of various tank varying sizes collecting rainwater from 10,000 m2 rooftop area of a college campus for the local historical dry, average, and wet years. Results show tank sizes of 130–630 m3 having 100% capture efficiency but system reliability varies from 2.8% to 37.75% in the dry to wet years, respectively. An optimal tank size range is derived from the reliability curves that represent the tank system performance in the local climate. Optimal tank size ranges from 180 to 240 m3, which can capture more than 64% of the roof runoff and thus the campus can reduce on an average 10% of urban water demand.