Every two weeks, go to top level of your house, fill up a tub of hot water.
Then release. If you do this every two weeks, you will flash out most things.
Then most likely, you don't need anything. Lol...
A few tricks to never clog your drains
1. use one ply toilet paper
2. never dump 有油脂的湯。放冰箱裏，然後刮去油脂再到
3. Use above method every two weeks
4. Never drop other objects into drain
