Rainwater Harvesting as an Alternative Water Supply for a Residential Building in Cavite, Philippines

Rainwater Harvesting Systems (RWHS) were investigated in the Philippines for domestic level as a supplemental water resource for non-potable water usage because of the country's geographic location. This study designed a RWHS for a residential building in Imus City, Cavite, Philippines. The RWHS is designed considering the Optimum Tank Size (OTS) and its corresponding water yield and the evaluation of its water saving efficiency (E
t
). The optimum tank size was obtained by using the Simplified Approach which is based on the Inflow Volume. In order to measure the monthly water yield (MWY) while only accounting for 38% of the household's 12-year water demand, the research additionally utilized the Demand-After-Rain (DAR) approach, which is a simulation equation derived in the unique scenario of the Yield-After-Spillage (YAS) algorithm. The peak water demand of the household is 45 m
³
but 38% of this was only used in consideration of non-potable uses only. The RWHS tank supplied a peak monthly yield of 12.88 m
³
during the rainy season. The efficiency of the tank ranged from 28.45% to 48.74%. Moreover, the water saving efficiency of the tank was observed to have an average of 39.18% for the year 2010-2021.