Do you know that regularly running boiling water down your drain is perhaps the best way to keep it clear and functioning well? Since the drain’s worst enemy is greasy deposits, make sure you don’t pour messy grease down it.
Try this foaming drain cleaner: take 200 g. baking soda, 100 g. table salt and 200 g. of vinegar. When the alkali (baking soda) meets the acid (vinegar) they will bubble furiously, and push the abrasive salt through the drain. All these safe and cheap cleaners will wash out the curdled mess from your drain. After 20 minutes pour boiling water down the drain to flush it clear. Remember that chemical drain openers are highly corrosive and dangerous to use. Their main ingredients are sodium hydroxide (lye) a caustic that can burn the skin and cause blindness if it gets into your eyes, and sulphuric acid, a corrosive chemical that can cause severe skin burns and blindness.
from: What’s In This Stuff? by Pat Thomas. The Essential Guide to what’s really in the products you buy.