How to clean a Septic Tank naturally? Adding yeast and sugar into the septic tank work very well to clean the Septic Tank Naturally which activates enzymes and promote the “good” bacteria. These bacteria help in cleaning up the dumped to large extent. Here are the ways how to clean a septic tank naturally.  Things required for cleansing: 2 cups brown sugar 6 cups warm water or 1/2 gallon of water  4 T’s baker’s yeast Pour the solution of sugar and yeast into the water.  Before hitting the bed make this solution and pour it inside the toilet and flush…