How a septic system works
A conventional septic system has two main parts: the tank and the drain field (also called a leach field or soil absorption field). Wastewater from the house flows into the tank, where solids settle to the bottom as sludge, and fats, oils and grease float to the top as scum. Bacteria break down some of the solids. The liquid in the middle, called effluent, flows out to the drain field, where it soaks into the soil, and the soil filters and treats it further.
Over time, sludge and scum build up in the tank. If they aren't pumped out, solids can flow into the drain field and clog the soil, which is the most common way drain fields fail. Pumping is the single most important maintenance a septic system needs.
How often to pump
There's no single schedule for every home. The right interval depends on the tank size, the number of people in the house, how much water you use, and whether you use a garbage disposal. The U.S. Environmental Protection Agency's general guidance is that household septic tanks are typically pumped every three to five years, and that systems should be inspected regularly. A contractor who measures the sludge and scum layers during pumping or inspection can recommend a schedule for your household.
What happens during pumping
1. The technician locates and uncovers the tank lids. Many tanks are buried; risers that bring the lids to the surface make future service easier and cheaper. 2. The tank is pumped through the main access, ideally the large manhole rather than a small inspection port, so the whole tank can be cleaned. 3. The technician checks the inlet and outlet baffles or tees, which keep scum and solids in the tank. A missing or broken outlet baffle lets solids escape to the drain field. 4. If the tank has an effluent filter, it's cleaned. 5. The technician looks for cracks, signs of groundwater entering the tank, roots and backflow from the drain field. 6. You get a record of the service, the sludge and scum levels, and any problems found.
Keep the records. They help plan the next pumping, and they're valuable when selling the house.
Habits that protect your system
- Spread out water use. Fix leaking toilets and faucets, use high-efficiency fixtures, and avoid running several loads of laundry on the same day.
- Flush only toilet paper. Wipes, including "flushable" wipes, paper towels, feminine products, dental floss, cat litter and diapers don't break down and fill the tank.
- Keep grease out of drains. Fats and oils add to the scum layer and can clog the drain field.
- Go easy on the garbage disposal. Food waste adds solids; homes with disposals usually need more frequent pumping.
- Avoid harsh chemicals. Large amounts of bleach, drain cleaners, solvents, paint and medicines can harm the bacteria in the tank and contaminate groundwater.
- Don't rely on additives. Septic additives aren't a substitute for pumping.
- Protect the drain field. Don't park or drive on it, build over it, or plant trees near it. Direct roof drains and surface water away from it.
Questions to ask
- How large is my tank, and how full was it?
- Are the baffles and effluent filter in good shape?
- Did you see any signs of groundwater, roots or drain field backup?
- When should I schedule the next pumping?
- Would risers make future service easier?