2. The water come out of the dishwasher is quite hot, so run the dishwasher regularly, Put some detergen in the drain when you run the dishwasher may help too.
3. Try not to use food disposal too much.
4. HD sells some kind of germ for septic tank care. I guess that is the stuff you are talking about.
5. 牡丹樓吃餅 please!