If your house is on a septic system, you may not realize how fragile that system is. Although it operates according to a simple principle, and it probably has few or no moving parts, it requires care and maintenance or it won't work properly. If something goes wrong, you'll notice symptoms both inside and outside your house, and when you do, respond promptly to avoid permanent damage to your tank, pump or drainage field.
How Your Septic System Works
Understanding how your septic system works helps you understand how it can fail. Water from your plumbing pipes passes through a 4- or 6-inch pipe to the septic tank, a large plastic or concrete holding tank buried near the house. Solid waste settles to the bottom of the tank while black water passes through an outlet pipe to the drain field. If the tank is located below the drain field, a sump pump inside the tank transfers the water to a distribution box, and from there it flows into perforated pipes and percolates into the ground. The system fails when blockages obstruct the pipes, tank or drainage field, or when the pump stops working.
Early Symptoms of Failure
The drainage field is the most vulnerable part of the system, and it's often the first part to fail. When it does, nutrient-rich sewage water remains near the surface of the ground, and the vegetation in that area thrives. You'll notice unusually green grass in an overflowing septic field, and if the problem isn't treated, sewage odors will also develop. When you go out there to investigate, you may note spongy ground and contaminated runoff coming from the field. If your system has a D-box, the problems are most likely to develop around it first, then spread to the rest of the drainage field.
Once a blockage develops in the drain field, pipes or tank, water from the tank begins backing up into your plumbing pipes. The blockage is usually partial at first, and you'll notice sluggish flushing from your toilets and slow draining from your sinks, tub and shower. If you don't do something about the blockage, water may eventually overflow from the lowest toilet or drain in your house -- if you have a shower or floor drain in the basement, it will be the first to overflow. The unmistakeable foul smell of sewage accompanies a severe backup, and you won't have any trouble detecting it.
Pump Failure and Freezing
If the pump in your septic tank fails -- which becomes increasingly possible as it ages -- the tank will overflow. When this happens, your plumbing fixtures won't drain properly, and the ground around the tank will become soggy and odorous. The vegetation in the drain field, instead of being lush and green, will die. Plumbing backups that occur in winter are often the result of frozen water in the septic pipes, tank or leach field. Your system is most likely to freeze if the weather is cold, the snow cover is light and you use the plumbing infrequently.