What is a septic system?
A septic system treats the wastewater from toilets, sinks, showers and laundry on your own land. Wastewater flows from the house into an underground tank, where solids settle and fats and oils float, and then the liquid moves out to a drainfield where soil does the final cleaning work.
Designs differ. Some systems use gravity, some use pumps, and some use added treatment units. Which kind you have, and what rules apply to it, depends on the state and county. Your county health department or the state agency that regulates septic systems can tell you what is allowed locally.
Think of it as a slow, quiet process. Nothing in a septic system happens quickly, which is why a problem can build for months before you notice it. That is also why regular care works so well.
What are the main parts?
The tank is a watertight container that holds wastewater long enough for solids to settle into a layer of sludge and for floating material to form a scum layer. Baffles or filters near the outlet help keep solids out of the drainfield.
The drainfield, also called the leach field, is a network of pipes or chambers in soil. Liquid spreads out and slowly percolates through the soil, where natural processes remove many pollutants. The soil itself is part of the treatment, which is why compacting it or flooding it causes trouble.
- Pipe from the house
- Septic tank with baffles or filter
- Distribution to the drainfield
- Soil beneath the drainfield
Why does what I put down the drain matter?
A septic tank depends on a balance of settling and natural breakdown. Grease, wipes, hygiene products, paper towels, cat litter, chemicals, paint and large amounts of bleach or disinfectant can clog the system or harm its function. Even products labeled flushable may not break down in a tank.
Heavy water use in a short time is also a problem. A day of many loads of laundry can push too much water through and carry solids into the drainfield. Spreading use across the week is kinder to the system.
Septic systems are built for ordinary household waste. A farm or home business that sends large amounts of wash water, animal waste or chemicals to the system may need a different arrangement, so ask your health office before adding any new use.
How do I find out about my own system?
Start with the county health department or the local permitting office. Many keep a record of the system with a diagram, the tank size, the install date and inspection history. If there is no record, a licensed septic professional can locate the tank and describe what is there.
Learn where the tank lids and drainfield are, and draw a map. Keep it with your house papers. Do not guess the location by probing with rods or digging, since you can damage the tank or pipes.
What should I keep off the drainfield?
Do not drive or park on it, build on it or plant trees close to it, because roots can enter pipes and weight can crush them. Keep roof gutters, sump pumps and surface runoff from flowing onto it. Grass is generally a good cover, but ask your health office or septic professional what suits your area.
Keep livestock off the drainfield as well. Hooves compact soil and manure adds to the load.
If your property has a pond, creek or well, ask your health office about required distances between the septic system and water sources. Distances are set locally and should not be guessed.
Who inspects and who regulates?
Septic regulation is mostly handled by states and counties. Some require permits for installation and repair, some require inspection at property sale, and some set rules for who may pump or inspect. Because requirements differ widely, ask the local health office rather than relying on advice from another area.
The EPA offers general educational guidance for homeowners, but it does not run your local program.
What are the first things to do as a new owner?
Ask for the records, learn where the parts are, have the system inspected by a licensed professional if its condition is unknown and ask about the right schedule for pumping. Keep records of everything, including receipts.
Talk with every household member about what goes down the drain. A few simple habits are the cheapest protection a system can have.
Key takeaways
- A septic system uses a tank and soil to treat household wastewater
- What goes down the drain affects the whole system
- Keep vehicles, roots and extra water off the drainfield
- Rules and records are local, so ask your county health office
Sources and further reading
Last reviewed: November 12, 2026. Written by the Rural Farm Life Editorial Team. See our editorial policy.