Check the distribution box located between the septic tank and the percolators. You’ll probably have to push harder and sharper to clear the blockage. Gain answers to common questions homeowners have regarding Asap septic can run a camera through the pipes and find out what’s causing the clogged sewer drain pipe. How to unclog main drain to septic tank . How to unclog a septic system drain. The septic tank or septic vents have frozen due to low temperatures. Ad over 85 million visitors. The septic tank vent is blocked; The septic tank or septic vents have frozen owing to lower temperatures. An additional way to unclog a septic tank drain pipe is by using a specialized tool that cuts up tree roots from drain pipes. Part of the drain inlet or outlet of the septic tank is clogged. The septic tank vent is blocked; The standard for septic tank maintenance recommends pumping out the tank every three years so that this doesn’t occur. Methods to unclog a main dra...