Concrete vs. Plastic Septic Tank: Pros, Cons, and When to Choose Each
Make a solid choice
Highlights
Plastic septic tanks are less expensive and easier to install than concrete ones.
Concrete septic tanks are more durable and last longer—up to 40 years.
All 50 states approve of concrete, but some states and local municipalities have restrictions against plastic.
A pro should evaluate your soil conditions, site topography, and local regulations to ensure the best choice.
Most septic tanks are either concrete or plastic. Concrete tanks are more durable and expensive, while plastic tanks are more affordable but more susceptible to damage. Depending on your property and needs, both can be great options for managing the wastewater from your home. Learn about concrete versus plastic septic tanks, their costs, and when to choose each.
Concrete vs. Plastic Septic Tank: Key Differences
Concrete septic tanks are more durable and last longer, but they're more expensive and difficult to install. Plastic septic tanks are more affordable and easier to install, but they aren’t as durable and don’t last as long. Unfortunately, plastic septic tanks aren’t approved in certain municipalities and areas due to potential floating and contamination. On the flip side, all 50 states in the United States approve of concrete septic tanks.
What Is a Concrete Septic Tank?
A concrete septic tank is made of precast concrete and reinforced with steel rebar. It’s a durable option that can last up to 40 years with the right maintenance. Concrete tanks are not susceptible to damage from ground shifts and roots, and there’s no risk of them floating out of the ground during heavy rains. Because concrete holds a large amount of effluent, you can pump your septic tank less often than if it were plastic. Concrete septic tanks weigh a few tons, so leave this job to the pros who have the special equipment needed to install them.
| Pros | Cons |
|---|---|
| Highly durable and damage-resistant | More expensive than plastic tanks |
| Long-lasting | Difficult to install; special equipment is necessary |
| Stable and resistant to shifting from environmental factors | Can suffer damage from groundwater contact if improperly installed |
| Minimal maintenance | More prone to cracking and more difficult to repair |
| Approved for use in all U.S. states | Fewer unique designs and sizes available |
Best for:
Homes you plan to live in for a long time
Areas with a high groundwater level
Areas with heavy rains, frequent ground shifting, or other harsh environmental conditions
"Concrete septic tanks are extremely resistant to buoyancy, so consider concrete instead of plastic if you live in a flood-prone area."
— Bethany Uribe, Division Manager/Estimator, ASAP Restoration LLC, Tempe, AZ
Pros of Concrete Septic Tanks
Concrete septic tanks are incredibly durable and resistant to damage from root systems, soil movement, heavy loads, and heavy rains. Unlike plastic tanks, which can float out of the ground during heavy rains, concrete septic tanks remain intact. They are also resistant to shifting and movement, which can damage your property and septic system. With regular maintenance and pumping, a concrete septic tank lasts up to 40 years.
Cons of Concrete Septic Tanks
Concrete septic tanks are heavier than plastic ones and are more complex and expensive to install. Heavy machinery, such as a crane, is often needed. Repairs are also more challenging, so you must keep up on septic tank maintenance. Concrete septic tank sizes range from 750 gallons to 2,000 gallons for residential properties. They only come in rectangular and cylindrical shapes and can be hard to fit into tight spaces.
What Is a Plastic Septic Tank?
A plastic septic tank, also known as a poly septic tank, is made of polyethylene and is a lighter, less expensive alternative to a concrete septic tank. Poly septic tanks are easy to install, resistant to damage from groundwater, and resistant to corrosion from acidic soil. However, they can shift and float up during heavy rains, which can cause severe damage to your system and property. Plastic septic tanks have a life span of up to 30 years.
| Pros | Cons |
|---|---|
| Less expensive to buy and install | Not ideal for locations with high groundwater levels |
| Easier to install; no heavy machinery required | More likely to float up and cause damage during heavy rains |
| Less prone to cracking, corrosion, and rust | May not be approved in your area or state |
| Easier to remove and replace | Not as long-lasting or durable as concrete |
| Hygienic and easy to keep clean |
Best for:
Homes without heavy vehicle traffic or high groundwater levels
New construction homes
Tight spaces and close property lines
Pros of Plastic Septic Tanks
Plastic septic tanks are less expensive to buy and install than concrete ones because they’re lighter and don't require heavy machinery to install. Additionally, they’re watertight, resistant to rust and corrosion from acidic soil and groundwater, and don’t crack as often as concrete because they’re more flexible.
Poly septic tanks are easy to move and can fit into tight spaces. They’re also easy to connect to plumbing due to their pre-installed inlet and outlet fittings. When it comes time to replace a plastic septic tank, costs are lower due to the ease of removing it.
Cons of Plastic Septic Tanks
Plastic septic tanks don’t last as long as concrete ones (30 years for plastic versus 40 years for concrete). They’re also not as durable, making them unsuitable for locations with heavy vehicle traffic. They can also float up during heavy rains, which can destroy your plumbing system and cause significant damage to your septic system. Not all states and areas approve of plastic septic tanks, so check with your local municipality or county health department to see if they’re an option in your area.
Concrete vs. Plastic Septic Tank
When deciding between concrete versus plastic septic tanks, consider the main factors, including geographical location, longevity, and cost. Here’s a breakdown of critical considerations (and which septic tank material wins in each) to help you make an informed choice.
Durability: Concrete Septic Tanks
Concrete septic tanks hold up better to soil movement, heavy rains, and vehicle traffic than plastic septic tanks. They are resilient and stay intact no matter the conditions. For a durable, no-fuss septic tank, opt for concrete.
Price: Plastic Septic Tanks
Plastic septic tanks cost an average of $500 to $2,000, while concrete tanks range from $700 to $2,000. The bigger cost difference comes with the price of installation. Labor on a plastic installation ranges from $1,200 to $3,000, while labor for a concrete installation can go up to $6,500. Keep in mind that plastic septic tanks need to be replaced about 10 years earlier than concrete. Still, plastic is the most budget-friendly choice overall.
Ease of Installation: Plastic Septic Tanks
Poly septic tanks are lighter, easier to transport, and easier to install. But you should still hire a local septic tank company to install yours. Proper depth, installation, and plumbing hookups are critical to a well-functioning septic system. Concrete septic tanks weigh a few tons, and pros often need special machinery for installation.
Ease of Repair: Plastic Septic Tanks
Concrete septic tanks are difficult to repair and often require pumping the tank. You can repair cracks in plastic with epoxy mix or a fiberglass reinforcing patch.
Maintenance: Concrete Septic Tanks
Thanks to their supreme durability, concrete septic tanks require little maintenance and checkups. Plastic tanks don’t need much septic maintenance either, but they need a closer eye and more frequent inspections to ensure they remain watertight and in place. Both need to be pumped every three to five years or more often, depending on the tank size, the number of members in your household, and your water usage.
Length of Life: Concrete Septic Tanks
Concrete septic tanks last up to 40 years, while plastic ones last up to 30 years. No matter what, you can extend the life of your septic tank with regular maintenance and avoiding things that don’t belong in a septic tank.
Location Versatility: Concrete Septic Tanks
All 50 states approve concrete septic tanks, while not all states and municipalities approve plastic ones. Work with a local septic tank company to evaluate your soil conditions, groundwater levels, topography, and local regulations. If your soil has a high acidity rate, it will corrode a concrete septic tank. Similarly, if you have high groundwater levels and heavy rain, a plastic septic tank can float up and cause misalignment, damaging your entire septic system.
Options and Customizations: Plastic Septic Tanks
Plastic septic tanks come in more shapes and sizes, including low-profile models, dome-shaped, and sphere-shaped tanks. They come in all different septic tank sizes, including standard 1,250-gallon and larger 1,500-gallon tanks. Plus, they’re easy to fit into tight spaces. On the other hand, concrete septic tanks are a bit more rigid in design options, with rectangular and cylindrical being the two main choices.
ROI: Tie
Depending on your geographic location and soil condition, both poly and concrete septic tanks can be a good investment. Both have an impressive life span and can be low-maintenance if properly installed. Consult a local septic tank company to help you determine the correct type of septic tank for your property and ensure it lasts for many decades.