The prime objective of the present study was to evaluate the habit of drinking water and its relation to the development of diseases in the population of Farmgate slum of Dhaka city. The study has been carried out to assess the present conditions of the water supply, water-borne disease, treatment pattern, sanitation, and their overall knowledge about sanitation. The methodology of this survey consists of practical field observation and field based data collection of water supply, water-borne disease type, treatment pattern and sanitation situation through Participatory Rural Appraisal tools and questionnaire survey. During the survey, data has been collected by using a well-structured questionnaire from each households of slum. In this study 100 personnel participated where 56% population was 18-40 years age range. Their education status was below secondary level (21%) and higher level was very low (6%).The results depict that the majority of the population suffered from water related diseases such as typhoid (23%), dysentery (24%), diarrhea (91%), cholera (16%), constipation (16%), jaundice (31%), amibiasis (15%) etc. For treatment of these diseases most of them went to retail pharmacist (52%) and others went quack doctor, registered doctor, homeopathic and ayurvedic treatment. They were suffering most in rainy season (53.5%). Lack of proper knowledge about hygiene, polluted water supply, unhygienic sanitation, extreme level of poverty, dispensing medicine without the prescription are the main causes for waterborne diseases in this slum. Besides Governments, every conscious people should come forward to help them.