Runoff is an important element in the water cycle. The process and the amount of runoff that occurs and the factors that influence it are very necessary as a reference to determine the potential for water availability, water management, land stewardship, and runoff water utilization policies. Smart tanks are facilities that function as rainwater reservoirs for collection and utilization, infiltration, and detention of rainwater. The Sentul City (SC) area is in the Bekasi Hulu watershed, the land area is 2905.33 ha, with planned use for built land 83.62%, green open space 14.37%, and blue open space 2.00% (1). The research objective was to determine the amount of peak runoff, and efforts to reduce it by harvesting rainwater using "smart tanks" in the urban area of Sentul City. Runoff analysis with the rational method. Calculation of parameter runoff uses spatial analysis for land use, drainage boundary, DEM analysis, and rainfall intensity distribution. The dual benefits of implementing smart tanks, apart from being a source of clean water supply and also reducing peak runoff in SC and Bekasi Hulu.