How Does Your Septic System Work?

Ever wondered how your septic system handles the wastewater that disappears down your drains and toilets? Your septic system works much the same way as a public sewer system, except that it treats your home’s wastewater on site instead of sending it to a public facility. Although there are many types of septic systems, all of them use a combination of natural processes and technology to treat wastewater from your kitchens, bathrooms and laundry rooms.

Everything that you flush or put down a drain is directed out of your house and into into your septic tank for treatment.

Septic tanks are water-tight containers whose job it is to hold wastewater long enough for it to separate into layers. Tanks are usually several feet underground and can be located and accessed through a manhole cover near your house. All wastewater that collects there begins to naturally separate into layers with the heaviest sinking to the bottom and the lightest rising to the top.

Scum: Fats, oils and other low-density materials float to the top.  

Solids: Heavier solids, such as human waste, sink to the bottom.

Liquid wastewater: This layer, which contains microbes and bacteria, stays in the middle.

When your septic tank is pumped, the primary purpose is to eliminate the scum and solids layers that the septic process cannot effectively treat. Removing this waste helps to keep your system in good working order.

As for the liquid wastewater, your system is designed to gradually release it as new wastewater enters. This is distributed through a network of pipes under the surface of your drain field (or leach field). By exposing the wastewater to oxygen and soil microbes, the liquid is naturally treated for contaminants, such as harmful bacteria. From there, the treated effluent water filters down into the ground and eventually merges with groundwater.

Since liquid wastewater is the only layer you want to move to the drain field, it is important to pump your tank at scheduled intervals to remove scum and solids. If systems are not pumped, these layers continue to build up, leaving less room for wastewater. An overloaded septic tank can lead to leaks, blockages and even backups.

Additionally, household wastewater contains disease causing bacteria and viruses as well as high levels of nitrogen and phosphorus. While well-maintained systems will remove most of these pollutants, poorly maintained systems can contaminate groundwater and spread disease.