Cambodia is one of the fastest growing countries in the world. However, there are still many areas where there is a lack of safe drinking water supply. In such a situation, "Clean Water Supply System" developed by Yamaha Motor company has been making a big contribution for people in emerging countries suffering from drinking water problems. Mongkul Borey Referral Hospital is located about 100 km away from Siem Reap (which is the capital city of northwestern Cambodia) and was established with the support of ODA from Japan. A number of patients and pregnant women are coming to this hospital from rural areas to see doctors and receive good medical care. "Yamaha Clean Water Supply System" is installed in this hospital. This system named "Slow Sand Filtration" is based on a water purification system found in nature. Raw water from rivers is pumped into tanks and purified through processes such as Physical filtration and Biological filtration. One of the strong points of this feature is the concept of "Sustainability for local communities by their own operation". This supply system has no need for filter exchange or maintenance by a professional engineer. The local community can manage it by themselves thanks to easy use system. The filtered water by "Yamaha Clean Water System" is mainly used in places such as operating room and obstetrics ward where sanitary water is always indispensably required. The use of water that has undergone a filtration process has also been adopted in the cooking process for hospital foods such as soup and rice. "Trusted water" supports not only medical aspects but also everyday essential necessities. Efforts of the Japanese company continue to contribute to the realization of sustainable life for everyone worldwide.