Pumping your septic tank is essential to keeping your septic system maintained and working properly for a long time. Each septic tank is designed to only have a specific amount of wastewater when operating properly.
Typically for a 3 bedroom 2 bath home you will have a septic tank that has a working capacity of around 1,000 gallons. When operating properly your tank will look full but it should maintain approximately 9 inches of free space from the top of the tank to the top of the scum layer. The 9 inches of air space allows the movement of water to flow freely from the tank to the leach field.
Your tank should have a scum layer, wastewater, and sludge as seen below in the diagram. As you can see the sludge and scum layer are important to keep maintained and at normal operating levels. If not maintained the sludge and scum layer rise until the wastewater backs up into the home through the sewer line.
The scum and sludge layers can also build up to a point that they begin to enter into the leach field. This material in the leach field can create a biomat and allow the sewage to surface in your yard. When this happens most homeowners realize they need a septic pump. According to the NC Cooperative Extension the tank should be pumped if the sludge layer is built up within 25 to 33 percent of the total volume of the septic tank.
Most people don’t want to measure the amount of sludge in the bottom of their septic tank and that is why they came up with recommending pumping your septic tank every 3 to 5 years depending on use.