Due to the event of hazardous chemical injection into a water storage tank in Hongseong, Chungcheongnam-do in 2012, the Korean Ministry of Environment has revised the enforcement rules of the Water Supply and Waterworks Installation Act to install surveillance equipments such as closed-circuit television(CCTV). However, the enforcement rules still do not provide concrete provision for installation of physical security equipments. Thus we studied vulnerability of small-scale water supplies in Korea and developed guidelines for the physical security system of the facilities. The guidelines include selection and recommendation of the physical security approaches and measures to detect, delay and response to the presence of an intruder in small-scale water supplies. The security features include protection utilities(e.g., fencing and fence topping), exterior intrusion detectors and alarms, locks and padlocks, surveillance utilities(e.g., CCTV), and others.