I have lived in homes with septic systems (parents home) and sewer system (my first home) but never really paid them any mind until the purchase of our second home.
Our current home currently resides outside a township without access to a sewer system and was built with a Septic System.
In coming up with a design for our backyard I dug up my septic system permit 
to gather the proper information on our septic system.
If you need help reading your septic permit, you can check out our article here.
Septic System
A septic system consists of a septic tank, distribution box, and leach/drain field. The septic system takes all water and waste from your home’s pipes and allows it to filter out naturally through the sand, gravel, and soil.
Septic Tank
A septic tank is a watertight container that holds the wastewater from your home allowing time for the different elements to separate. In my case, the septic tank is made of concrete but there are options for fiberglass, steel, plastic, and aerobic.
The septic tank size is dependent on the size of the home as well as the lot size in which the septic system is being installed. To learn more about septic tanks, check out our article that goes into more detail here.
Distribution Box
The distribution is not present in all systems but it is in ours. The distribution box is a key component on the systems in which they are present.
The purpose of the distribution box is to help distribute the wastewater evenly amongst the drain field lines. The distribution box needs to be level in order to ensure proper function.
We ran into an issue where this was not the case early on and we ended up with a smelly puddle in our backyard but was a quick fix for the original install crew.
Leach Field or Drain Field
Once the wastewater (effluent) has worked its way through the septic tank and the distribution box it then navigates its way through the drain pipes in the drain field.
A leach field or drain field is a set of perforated pipes underground, either in one big area or in a set of trenches with gravel that is then covered in a layer of soil.
As the effluent works through the piping it then is discharged into the gravel and soil which helps filter out the bacteria and chemicals before working its way into the groundwater.
How does a septic system work?
All of the piping in your home converge into the septic system, from the toilets, showers, and sinks. Once the wastewater enters the septic tanks first chamber the products separate.
The wastewater separates into three distinct layers; the sludge layer, the scum layer and the effluent layer in between. After the wastewater fills in the tank it exits through the outlet pipe through a filter.
After working through the filter, the distribution box fills and disperses the effluent through the pipes in your leach field. As the effluent works through the piping it then filters through the gravel and soil.
Sludge Layer
The solid waste sinks to the bottom of the first chamber commonly called the Sludge Layer. This contains your human waste as well as any food waste and other solids that may make it through your drains.
If your system does have the proper bacteria amount, the sludge layer will also contain the waste from their work. As this material collects over the years, most homeowners will need to have their tanks pumped.
I have found on rare occasions, usually on forum posts, that some home owners claim to have been in a home where they haven’t pumped their tank in over 15 years. Typically this is not the case.
Scum Layer
The scum layer contains the particles that will not sink and float on top of the effluent layer. This typically contains fats, grease, and oils. It could also contain hair and fibers from the occupants typically from personal grooming and washing of clothes.
This is where you as a homeowner need to take care in the cleanup of your meals as well as other disposals you may have done back when you were on a sewer system.
Effluent Layer
The Effluent layer makes up a majority of the septic tank and consists of the wastewater that actually makes its way into the leach field.
As the septic tank fills and the effluent is dispersed through the chambers it will make its way to the level of the output which contains a filter.
Septic Tank filter
Before the wastewater makes its way into the drain field it must first go through the septic tank filter.
A septic tank filter is a plastic device that sits inside the outlet baffle preventing the few solids that did not sink to the bottom of the tank.
The purpose of the septic tank filter is to help prevent your leach field from being overloaded with solids that could limit the life of your system.
The septic system flow
Still not clear how things flow? Here are a few examples of how different daily events affect your septic system.
Septic system flow for toilets
When using the restroom at home, you typically send liquid and solids into your septic tank. The feces and toilet paper sink to the bottom of the tank in the sludge layer where the bacteria goes to work.
The urine and water fills the effluent layer until it reaches the filter. If it is already at that level then the addition of that flush disperses some of the effluent through the filter and into the distribution box.
Septic system flow for washing dishes (sink or dishwasher)
When washing dishes you may not think much about the flow of your septic system, but you should. When washing dishes in your sink do your best to scrap your dishes of left over food.
Any food that makes it’s way in your tank will take time to break down and will increase your sludge layer and could shorten the time between tank pumps.
It’s not just the food however to worry about here. Oils and grease that make it into your septic system they float to the top as part of the scum layer.
Septic system flow for washing clothes
When your washing machine finishes it cycle and drains it will disperse the water with chemicals, lint and fibers.
As the water drains into the septic tank, the lint and fibers float to the top scum layer while the water fills the effluent layer.
Septic system flow for bathroom sink tasks.
Whether it’s shaving, brushing your teeth, or trimming your nails, if it makes it into your sink drain it will make it into your septic tank.
Because human hair contains oil it floats and it will become part of the scum layer.
Related articles…
If you liked this article and are interested in more, check out our article 5 Common Septic tank questions answered for you.
Also available is our article on How to read your septic permit.