Why should we not allow our household drainage water to flow into nearby water bodies ?

We should not allow household drainage water to flow into nearby water bodies because it contains organic wastes, disease-causing germs and harmful substances. These pollutants contaminate water, make it unsafe for drinking and increase the risk of water-borne diseases such as diarrhoea, typhoid, cholera and dysentery. The polluted water can also harm aquatic life. Therefore, household drainage water should be properly treated before disposal.