Since 2014, a well-designed rainwater for drinking (RFD) project has been successfully operating at Cukhe Elementary School, near Hanoi, Vietnam. During that time, daily rainfall data, water consumption, water quality and questionnaires to the community were prepared. Several concerns over the design and operation of RFD projects, such as lack of sufficient rainfall data, water quality concerns, and public acceptance, are identified and overcome. Modeled results from using observed daily rainfall data, and using a simplified method from insufficient monthly data, are compared. The simplified method using insufficient rainfall data is acceptable for design within the error range of 0–11%. Rainwater quality after the use of the point of use treatment device proved that a well-designed rainwater harvesting (RWH) system ensures safe drinking water, which complies with WHO and Vietnam drinking water quality standards (VDWQS) guidelines. The people of the community liked the RFD system because of the satisfactory water quality and the economic benefits of not needing to purchase bottled water. The success of the RFD project at the Cukhe Elementary School proved the potential of promoting rainwater as drinking water in rural areas in developing countries, where a safe drinking water supply is a challenge, and should be promoted as an important means to achieve Sustainable Development Goal 6.