The septic tank appears simple at first glance but in actuality provides a simple and elegant means of achieving several complex actions. The tank itself fills with liquids fairly quickly, generally in a few days to a week. This does not mean that it's time to have your tank pumped out.
Solid matter entering tank slowly settles to the bottom of the tank if it's heavier than water or floats to the top if it's lighter than water. Fats and greases will tend to float Some solids create problems. Vegetable material contains celulose and is not readily digested by the bacteria in the septic tank. This causes solids to accumulate more rapidly. For this reason, garbage grinders are not recommended for homes having onsite sewage systems. Excessive hair is potentially problematic solid. Hair is generally neutral in bouyancy and neither floats or settles and presents clogging problems when present in large amounts.while most of the other solid matter will settle. Anaerobic (without oxygen) digestion takes place and most of the solids are converted to carbon dioxide, water and other byproducts. The process is not completely efficient and solids will accumulate over time