Septic tanks are one of the most crucial components of wastewater management for homes which are not connected to a municipal sewerage system. If you do happen to own a property with a septic system, or are planning to install a septic system, you’re likely wondering “how deep is a septic tank?”. The depth of a septic tank will impact everything from the installation costs to the maintenance and repairs of your septic system.
In this full-scale guide, we’ll cover:
The standard depth of a septic tank
Factors that determine how deep a septic tank is buried
How to locate your septic tank
The impact of depth on maintenance and pumping
Septic tank installation best practices
The depth of a septic tank will largely depend on a few different factors, such as soil conditions, the type of septic tank, your climate, and your local regulations. With this being said, most septic tanks are buried between:
•4-6 feet deep from the ground surface, to the bottom of the tank itself
•The top of the septic tank is commonly 1-4 feet below the ground surface
•The inlet pipe (where wastewater enters the tank) is typically 12-36 inches below the ground level
|
Septic Tank Type |
Typical Depth (Feet) |
|
Conventional Concrete Tank |
4 – 6 feet |
|
Plastic or Fiberglass Tank |
3 – 5 feet |
|
Low-Profile Septic Tank |
2 – 4 feet |
|
Mound System Tank |
1 – 3 feet |
|
Deep Bury Septic Tank |
6 – 10 feet |
Multiple factors will influence how deep a septic tank needs to be buried, which includes soil conditions, local climate, local regulations, and tank type.
Septic tanks have to be buried within well-draining soil, as this allows for proper filtration of any wastewater in the drain field.
Clay soil will hold water quite well, so septic tanks will need to be buried shallower to prevent backups.
Sandy or gravel-based soil allows for better drainage, enabling the tanks to be buried deeper
Each individual state and county has specific requirements for septic tank depth
Some areas may even require a specific minimum depth to prevent freezing of the tank, especially in colder climates
Inspectors may mandate a specific depth in which the septic tank has to be buried based on the soil and water table levels
In cold climates, septic tanks will be buried deeper (about 4-6 feet deep) in most cases to prevent freezing
In warm climates, septic tanks will be buried at a shallow depth (3-4 feet deep) without having to run the risk of freezing
A higher water table (nearby lakes, rivers, or marshlands) could limit just how deep a septic tank may be placed.
A shallow burial prevents groundwater contamination, yet it may require a much more strategic and careful design
Concrete septic tanks are much heavier than plastic or fiberglass tanks and can be buried deeper due to their increased levels of durability.
Plastic or fiberglass tanks are lighter than their concrete counterparts and can be buried at a more shallow depth to prevent floating.
If the soil surrounding your septic tank does not drain well, mound systems may be required, which bury tanks only 1-3 feet deep.
Shallow-bury septic systems are often used when the groundwater levels are too high
If you need to locate your septic tank, whether you’re pumping your septic tank, maintaining your septic tank, or inspecting your septic tank; below you’ll find a few effective methods for doing so:
Your local health department will likely have some form of a record indicating your septic system’s installation depth and location.
Within your home, you’ll be able to locate the main sewer exit pipe (commonly found in the basement crawlspace).
Follow the pipe straight into your yard, and your septic tank will be located about 10-25 feet away from that location
Septic tanks will often be covered with some soil, but not inaccessible in most cases
Through utilizing a metal probing rod, you can carefully locate the tank by feeling for a hard surface
If you begin to notice greener grass, or even a slightly raised ground, this could indicate the location of the septic tank itself
Areas which are soggy or present cases of standing water could suggest a full septic tank, or a failing system
If you are unable to locate your septic tank, a septic service company will likely be able to locate your septic tank with the help of electronic locators or ground-penetrating radar.
The depth of your septic tank will impact how easy or difficult it is to access for septic pumping and repairs.
•Shallow-buried septic tanks are easier to access for both pumping and inspections
•Less excavation required in the event repairs are deemed necessary
•Could possibly freeze in colder climates, due to the shallower depth
•Standard depth septic tanks are protected from most forms of surface damage and temperature fluctuations
•Generally meets the standards of most local building codes
•Requires some excavation for maintenance and repairs
•Deep-buried septic tanks are quite protected from freezing and surface disturbances
•Typically more difficult and expensive to pump and repair in most cases
•Could possibly require a riser installation for easier access
A septic tank riser is a vertical extension which allows for easier access through the bringing the septic tank’s lid closer to the surface, allowing for easier repairs and maintenance
•Reduces excavation costs during pumping
•Saves a lot of time with maintenance and repairs
•Helps to prevent damage to landscaping from excavation efforts
If your septic tank is 3-6 feet underground, a riser should extend at a minimum of around 12-24 inches above the ground
This will allow for easier access while still blending into the yard seamlessly
If you're installing a brand new septic system, below you’ll find some important guidelines which will help to ensure a proper burial depth:
You should always check with your local health and safety department prior to installing a new septic system
Obtain the proper permits and approvals to ensure you’re complying with local laws and regulations
Avoid installing your septic tank system near any high water table areas to proactively prevent any system failures
Install the septic tank at least 10-25 feet away from your home
Ensure it’s kept well away from driveways and tree roots
Ensure the inlet and outlet pipes are positioned correctly
Level the tank to prevent any unwanted drainage issues
If your septic tank is buried deeper than 3 feet, consider installing a riser
A riser will allow future septic pumping efforts to be much faster and more affordable in most cases
Schedule a septic tank inspection around every 1-2 years
Pump the septic system every 3-5 years, depending on overall household usage rates
Many septic tanks will be buried 4-6 feet deep, yet your septic tank’s buried depth will depend on the soil conditions, the local climate, the local regulations, and your septic tank type. Through knowing how deep your septic tank is buried, you’ll have a better grasp on what’s needed for septic tank maintenance, repairs, and future upgrades should you choose to do so. If your septic tank is buried deeper than 3 feet, you should consider installing a septic tank riser for easier access when it comes to pumping and repairs. When you follow proper installation guidelines and adhere to best practice when it comes to maintenance, you’ll find your septic system will be able to function efficiently and effectively for many years to come.
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