1) Cooking oil and fats should not be thrown down the drain. They can harden and block the pipes. In an open drain the fats clog the soil pores reducing its effectiveness in filtering water. Throw oil and fats in the dustbin.
2)Chemicals like paints, solvents, insecticides, motor oil, medicines may kill microbes that help purify water. So do not throw them down the drain.
3)Used tealeaves, solid food remains, soft toys, cotton, sanitary towels, should also be thrown in the dustbin
These wastes choke the drains. They do not allow free flow of oxygen. This hampers the degradation process.