Eliminate drain odors naturally by pouring half a cup of baking soda down the drain followed by half a cup of white vinegar. The fizzing reaction breaks up organic buildup causing the smell. Wait 15 to 30 minutes then flush with boiling water. Repeat weekly to prevent odor return. This method is safe for all pipe types including septic systems. For persistent odors the P-trap may be dry or the vent pipe could be blocked.