Here are steps to troubleshoot a standard gravity septic system:
- Open the lid of the septic tank and observe the water level.
- If the level is normal, then the problem is in the line inside the house or between the house and the tank. There may be a simple stop-up or clog, or the line may be broken down. A sewer snake can unstop a line, but if it is broken down then the failed piping must be replaced.
- If the level in the tank is high, then either the line leaving the tank is clogged or something is wrong with the drainfield. Possible problems include sludge in the bottom of the tank, biomat clogging, drainfield lines crushed by heavy vehicles, dislodged by shifting soil, or infiltrated by tree roots, or the field is saturated.
- Snake out the line leading from the tank to the drain field (leech field, leach field). If the snake comes back with mud, that suggests that the line is broken down.
- If lots of smelly water pours back into the septic tank when it is pumped, that tells you the drain field is saturated. Chances are it will need to be remediated or replaced.