How Does A Septic Tank Work?

A septic tank is not what most people want to talk about. But that doesn’t mean that they can be ignored. Proper care of your septic tank and septic system is crucial to your quality of life. Time to bite the bullet and learn.

how does a septic tank work

So it can be important to learn what you can to prolong the life of your septic system. After all, most people who aren’t on city sewage have septic systems. This number can only grow as more people choose to live a more rural life. 

What Is A Septic Tank?

A septic tank is an underground chamber made of a solid material through which wastewater flows and is disposed of. It is a simple wastewater disposal system often used in domestic cases and private homes.

A septic tank cannot operate alone and instead is part of a septic system. But even if you are installing a brand new septic tank system, it will be much cheaper than trying to connect to city sewage or another way of disposing of wastewater. 

How Does A Septic Tank Work?

How Does A Septic Tank WorkView in gallery

If you’ve ever wanted to learn how a septic system works, then you are at the right place. The sewage that enters the septic tank is partially decomposed by bacteria which makes it easier to transfer and settle.

We call the decomposed matter sludge that settles to the bottom of the tank. The parts that can’t decompose properly float to the top which forms what we call scum. These two materials have a water layer in between them.  

The purpose of the septic tank is to slow down the movement of raw sewage and wastes. Without it, the sewage would be transported directly into the ground, which isn’t safe or healthy for humans.

The Absorption Field

The absorption field is another part of the septic system. Excess water flows out into the field after it goes through the septic tank. The soil needs to be percolated and now a solid and packed soil like clay. 

Extremely loose soil like sand is also not appropriate because the water can’t flow through and be absorbed properly. So something in the middle is perfect. Another name for the absorption field is the drain field.

Septic Tank Diagram And Parts

Septic Tank Diagram And Parts

Now, let’s take a look at the septic system and the parts that make up a septic tank. Because learning each part of the septic tank can help you learn how to care for your septic tank and give your system the longest life possible. 

Input Baffle

The input baffle is where the sewage enters from the house. This pipe is connected to your plumbing directly. Anything that drains outside is usually connected to this input baffle pipe. This can also be called the inlet baffle. 

This is usually made of a pipe that matches the pipe connected to the house. This pipe is hidden and can only be accessed by a professional. A blueprint of septic pipes should be kept on hand if possible. 

Output Baffle

The outlet baffle is the area and pipe where the wastewater goes to the drain field or absorption field. This is how the wastewater escapes and how the septic tank doesn’t overflow. Though a low capacity tank may struggle even with this output.

The output pipe usually contains a filter that will ensure that nothing exits the septic tank that isn’t cleaned. Because if contaminated water enters the drain field, it could cause a hazardous domino effect. 

Scum Layer

The scum layer is made up of the non-decomposed matter that floats to the top of the tank. Gasses that the sludge layer creates will also float to the top of the tank. This is called the scum layer and it is visible from the inspection pipes.

The scum layer is partially filtered out of the septic tank with the wastewater. It can also be skimmed out during inspection to pumped out when the sludge layer and wastewater are pumped out.

Sludge Layer

The sludge layer is made up of decomposed matter that goes through the sewage system and enters the septic system. This sludge is eventually cleaned up and pumped but settles on the bottom while evaporating. 

Yes, the name sludge layer is quite stomach-turning, but it is an accurate description. Removing the sludge layer is important when the septic tank is pumped out every few years. 

Inspection Pipe

The inspection pipes allow professionals, or you, to view the levels of the water and scum in the septic tank. You can lift the lid and view it at any time which will let you know when you need to pump the tank.

The inspection pipe is only a few inches wide and has little use except to view the septic tank without having to dig it up. Digging it up may need to be done if the manhole is buried without a large pipe attached. 

Manhole Cover

The manhole cover is large enough for someone to fit into. However, it should not be used except by a professional to inspect the tank or to pump it out. That is the use of the manhole cover, so try to leave it alone. 

The only thing you need to check for if the manhole is visible is leaks. Leaks could indicate that the manhole isn’t secure well or that the septic tank is overfilled. Both are problems that need to be addressed. 


The wastewater level is the water that is passed through the plumbing system. This is the water that will enter the wastewater drain field. It has been filtered and will be safe for draining into the field. 

Any water that you flush down the toilet or drain ends up as wastewater. The wastewater will disperse into the ground but overfilling the tank will disrupt this process, so it’s important that the tank is big enough.

Septic Tank Safety Tips

Septic Tank Safety TipsView in gallery

Septic tanks can be dangerous if not handled properly. So take heed and use these tips to ensure you keep your family safe and healthy when dealing with a septic tank system, especially if it is private.

For best results, ensure that you only let a professional deal with the septic tank and only notify them if there is a problem. Don’t forget to also keep your appointment for the yearly inspection and keep the tank pumped. 

Never Enter The Septic Tank

Again, the manhole cover may be tempting if you want to inspect your own tank, but it should never be used by you. So never enter your tank under any conditions. Professionals have special gear to protect themselves. 

Don’t Place Under A Structure

When placing your septic tank, never place it underneath a deck, patio, or any type of structure. It is important that the tank is easy to access. If you cover it, then it cannot be pumped or repaired properly when the time has come. 

Stay Above 1,000 Gallon Capacity 

Even if you live alone, using a tank that has less than 1000 gallons capacity can be dangerous. Use the 1000 gallon minimum unless a professional says you can use less. If you have more than 3 bedrooms, use a larger one.

Pump The Septic Tank Every 1-4 Years

Your tank should be inspected about once a year, but it should only need to be pumped about every 4 years or so. The professional will let you know when you will need to pump it during his yearly inspection. 

Don’t Let Food In

Only waste should go in the septic tank. Avoid using garbage disposals if the sink drain is set to enter the septic tank. No oils, foods, or objects should enter the tank unless they are meant to enter the tank.

Conserve Water

Don’t use any more water than you need to use. Leaving water running or taking excessively long showers will just ensure that you need to pump your tank every year. So, avoid this by conserving water. It’s good for your wallet and the environment anyway! 

Watch For Groundwater Contamination

This is an important thing to do. Ask the team that inspects your septic tank to also check the water around the drain field. If it is contaminated then the filter isn’t working properly and could cause health issues. 

Related: Septic Tank Treatment Options You Can Do Yourself

Should I Install A Septic Tank?

Asking for advice from a professional in your area is probably your best bet. But an even better place to start is the neighbors. Ask your neighbors what they use and if they have had any problems with their systems.

Chances are, using the same as they do is your best bet. However, if you don’t have any neighbors, then there’s a really good chance that a septic tank is your only real option. So call a professional to set an appointment up.

After that, there is little for you to do because the company installing the system will do all of the work, get permits, everything. So leave it up to them and rest easy knowing it will all be taken care of.