In Bangladesh, there are a consequential proportion of the population is without access to salubrious water sources and to lead a healthy and productive life humans need a salubrious source of water is a requisite. To consummate the deficit of salubrious water rooftop rainwater harvesting (RRWH) can be the alternative to underground water. RRWH can be legitimated as an appropriate alternative for groundwater because of the lofty yearly precipitation rate in Bangladesh. In addition, there is a massive gap between requisite and repository for fresh water and the situation seems vulnerable that can be deteriorated in the future. The current situation is distressful and this challenge needs to sort out properly otherwise it can prove a threat to mankind. Perhaps, as the present and future of the treatment of surface water is not blazing and the dependency on groundwater has to lessen so RRWH can be proved as the potent alternative. This study investigates the reliability, applicability of RRWH systems using daily water balance for an educational institute. The reliability co-relations with the different tank volumes indicate that both the time base and volumetric reliability rise with the increase of tank volume. Reliability does not rise with the upsurging consumed water value. But both time-based reliability and volumetric reliability lessen with the upsurging water demand. It can also be observed time-based reliability is greater than volumetric reliability and the overflow ratio decreases with the increases of tank volume. Besides, average water-saving increases with the increase of tank volume. RRWH has the potential to solve the water deficit problem in an educational institute for toilet flushing and floor cleaning purposes by meeting 22354 lit/day water demand.

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