How Septic Systems Work

1. The main drain pipe from the house connects to the septic tank, which has a removable cap for cleanout.

2. In the tank, solid waste sinks to the bottom while oil and grease ride on the surface of the water in the middle. The water will be dispersed through the pipes, but the top and bottom layers need to be pumped out every two to three years.

3. The graywater leaves the tank and travels through a pipe to a distribution box.

4. The flow of sewage water carries it into perforated pipes called fingerlets, which carry the water to the drainfield (sometimes called a "leachfield"). Once in the soil, bacteria breaks down the remaining waste in the water.

5. The pipes must be buried at the correct depth to prevent sewage water from contaminating the area groundwater.

Septic tank graphic

Hiring a Septic System Installer

If you hire a company to install a septic system, these steps would likely be taken:

Obtain permits: Before installation begins, the necessary permits required in your area need to be secured. The contractor you hire should do this task. If the contractor fails to do this, you could find yourself having to tear out the tanks and pay hefty fines.

Survey the field to be used: The plumber or septic contractor will perform topography surveys of the area and complete a blueprint and project plan to ensure that your new septic tank will be positioned properly. Local zoning ordinances may require the septic tank be placed a set distance from structures and/or the property line.

Excavation and site preparation: This includes bringing in sand and gravel for the leach field. Accurate site prep is essential for the system to work properly since the force of gravity provides the necessary flow.

Stub out the plumbing: The term "stubbing out" refers to having a building's plumbing in place, but capped at various points awaiting installation of fixtures. So at this stage the plumber installs the drain from the house to the septic tank, ready for connection. The pipe needs to have the correct "fall," or degree of decline over distance to use gravity. If a toilet or sink is installed in the home's basement, a sewage sump pump must be installed and piped into the main drain.

Install the septic tank: When the plumbing field is ready the septic tank is installed.

Connect the tank to the plumbing: The piping that runs from the interior plumbing system of the home out to the septic tank will be connected and sealed to prevent leaks. Any drainage pipes that are necessary to connect to a secondary drainage area to prevent excessive pooling of water will also be connected at this point. The system will be tested to ensure that it operates properly. Once all connections are completed, the septic field will be filled in to hold the tank in place and provide proper operation of the septic system.

How Much Do Septic Systems Cost?

The average septic tank cleaning costs a few hundred dollars. Replacing a system can cost anywhere from $5,000 to $10,000, experts say.

Proper cleaning and maintenance is crucial in preventing small problems from becoming major, costly and messy disasters. 

Common Problems of Septic Systems

As with urban sewer systems, the house's main drain or pipes entering the septic tank could become clogged and cause a backup. Wastewater can come up through the sink drains, bathtub and shower drains, toilets and even washing machines.

Homeowners can decrease the chances of this happening by monitoring the items that are flushed through the plumbing system. Items such as oil or grease, cotton, diapers, gauze, cigarette butts, tampons, paints and other such items that do not break down easily should never be put through septic systems.

Septic systems can be disrupted by tree roots or other obstructions, and because they cover a lot of area, homeowners sometimes accidentally damage their own pipes by digging in the wrong location.

Septic System Maintenance

Septic systems are designed to separate sewage into three parts — solids, sewage water and the grease and oil that float on top. Only the liquid is distributed through the leach field so the solids and grease accumulate in the tank and must be sucked out periodically by a septic cleaning company. The frequency of cleaning could range from one to five years or more depending on how much it is used.

The septic tank should have an access cover or standpipe to allow for pumping. However, if there is no visible access, the tank must be located, which is usually accomplished by digging up the suspected area with a backhoe. If digging is necessary, provisions should be made at that time for future access.

After gaining access to the septic tank, the sewer service removes the sludge from the bottom of the tank using a truck mounted pump and holding tank. The service company transports the sewage to an approved waste facility.

More Septic System Resources

Leave a Comment - 5


william Karslo

Subject: septic system installation

septic system over 50 yrs old tank filling up monthly

billy mac

Subject: great company , they send

great company , they send reminders, always neat


Subject: Drainage

Do the clogs ever get backed up and then something bad happens?

Robyn Fillman

Subject: Septic systems

Where are the motor, aeration & filter bag mechanisms located? What do they do? How often do they usually need to be replaced and what can go wrong with them?
How does one know if their service provider is being honest about what needs to repaired or serviced in regards to frequency?

Garry Annibal, REHS

Subject: Septic System guide

Your guide to septic systems is misleading. It says the effluent from the septic tank is "graywater". In the fields of public health, plumbing, environmental engineering, etc., graywater refers to the wastewater from sinks and laudry. It does not contain significant amounts of pathogens as does the effluent from a septic tank. Graywater may disposed of differently than septic waste. I think the guide should be reworded.
Garry Annibal
Harding Township Health Department

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