Whether you’re looking for a water tank or a septic tank, you’re likely dealing with two options for materials: plastic (specifically, polyethylene) and concrete. Both have their ups and downs, but most of the decision comes down environmental conditions—namely, the financial, logistical, and climate factors that are unique to each property.
It’s never a bad idea to hire a professional to make a recommendation that suits your needs. Septic or water tank technicians can provide an objective analysis as to which kind of tank would best fit your home or property. It will also be worth your time to familiarize yourself with the key differences between plastic and concrete. With the amount of money, time, and effort involved in installing a concrete or poly tank, there’s just no sense in taking any shortcuts. Here we’ll go over the advantages and disadvantages of both plastic and concrete tanks, hopefully providing you with enough information to make a decision about which type of tank to get.
Concrete is a highly durable material that’s been used in construction for centuries. Favored for its strength and resilience, concrete can be fashioned into pretty much any shape, allowing builders to make sturdy tanks, structures, and foundations that hold up to both geological and environmental pressures.
When buried underground, concrete tanks can resist ground shift. Because they’re so heavy they can be expected to sit where they were originally planted and remain in place for decades to come. Vehicles can drive over the soil above a buried concrete tank, and nearby trees can grow their roots without worry of penetrating or warping the structure.
For the same reason that concrete is highly resilient, it requires little maintenance. (However, the difficulty and frequency of repairs often depends on where and how the tank is installed.) When it comes to storing drinking water, concrete has considerable thermal mass, which helps to keep stable temperatures whether stored above or below ground.
Concrete’s strengths are also its weaknesses. The material is resilient largely because of how heavy and massive it is. So much weight is a hassle for transportation and installation, and can hike up your costs considerably. Installers will need to use heavy machinery to crane a tank into the desired location, and leaks cannot simply be remedied by lifting the tank out of the ground to apply a quick sealant. Repairers will likely need to dig through the ground to reach the source of the leak.
While concrete can last for decades, once it starts to degrade it presents all sorts of problems that are not easily remedied. As concrete ages it becomes more and more vulnerable to cracks and erosion, which will in turn cause the tank to leak. Again, these leaks are not easily fixed, especially when the tank is buried underground, and they’re certainly not inexpensive. If you’re dealing with a concrete septic tank the risks are particularly serious, as cracks can allow untreated sewage or wastewater to leach into the surrounding land or even rise to the surface. Repairing a concrete septic tank is never a cheap project.
Concrete is more porous than plastic materials like polyethylene. That’s the main reason why cracks and leaks are more common as concrete ages, and also why repairs are comparatively expensive. Moreover, concrete is often seamed together with slabs that are poured and dried at different times. That presents all sorts of opportunities for cracks and vulnerabilities to form over time.
Proper maintenance can forestall some of these problems before they get out of hand, but the maintenance itself requires periodic inspections that can be quite pricey. And unlike cracks in plastic, which can be sealed with a basic sealant, fixing concrete usually involves drilling into and sealing cracks from the inside out. A really old concrete tank may turn into a game of whack-a-mole, with new cracks and leaks appearing all the time, leading to a point where the cost is no longer justified. Some owners may even have to install a plastic liner around the tank, which can further jack up costs while defeating the original reason for getting a concrete tank.
Lighter and watertight, plastic or polyethylene tanks are much easier and cheaper to install and fix. For those reasons alone, plastic is often preferred for both septic and water storage tanks. Plastic is also the most common material used for storing chemicals, fuel, and food syrups.
Unlike concrete tanks, which require heavy machinery to lift and transport, plastic tanks are lightweight and can be moved around with simple equipment. This makes them ideal solutions for septic treatment and water storage in remote areas where transportation costs are at a premium.
Plastic is also more resistant to cracking, so it won’t necessarily require routine structural inspections. Molded from a single piece of plastic, poly tanks have no joints, beams, or sealed components. Better yet, they are completely resistant to water-based damage. Whether installed in damp soil or above ground in a humid climate, plastic tanks will never corrode or rust. When they do crack, however, the fix is pretty simple: You merely apply some heat and some sealant to close the fracture. In some ways, plastic is more resilient than concrete precisely because of its flexibility. And when the tank’s life cycle is finally up, the plastic can be easily recycled.
While plastic is more flexible than concrete it is susceptible to cracking under intense pressure. Aboveground plastic tanks are especially vulnerable in extreme weather conditions and more likely to crack than concrete. This is an important factor to consider if your property is in an area prone to hurricanes, tornadoes, or wildfires.
Burying a plastic tank can save it from weather damage, but expose also it to some underground threats. Nearby trees can wrap their roots around or even puncture the surface of a polyethylene tank. When buried in an area with a high water table, plastic tanks can “float,” unleveling or even dislodging them from their intended location. Poly tanks may be more easily displaced than concrete, but neither is impervious to geological risks. Regions with a lot of seismic activity may pose threats in the form of earthquakes and ground shift.
Because plastic isn’t as resilient as concrete, owners have to be careful about how much weight is placed on top of them. That means plastic tanks can only be buried up to about three feet deep, and you’ll need to avoid driving or parking vehicles on the surface above the tanks. Too much weight can dent, warp, or even crush a poly tank. One workaround is to add a layer of corrugated metal to the exterior of the tank. This can help reinforce the structural integrity of the plastic and allow it to be buried further underground. It will also add weight to the structure and help resist damage from ground shifting. Of course, it will add to the expense of the project and present challenges to routine maintenance and repairs.
The pros and cons of concrete versus plastic tanks are more or less evenly split. That may or may not help you in your decision, but rest assured there is a whole industry of expert technicians and repair personnel who can help. Most people lean toward plastic because it’s cheaper, easier to install, and easier to repair—but that may not always be the case. If money is not a huge concern, or if you’re installing in a location with considerable environmental considerations, maybe concrete is the better option.
Whether the tank is meant to store drinking water or wastewater, there are all too many environmental factors you’ll need to consider. What works for one home may not work for another. Your best bet is to hire a pro to examine your location and offer some advice on which type of tank would work best for you.
Whether installing above or below ground, Go To Tanks has a huge selection of plastic storage tanks for virtually any purpose. Call 1-877-468-2657 and we’ll help you find a tank that fits your needs.
SALES@GOTOTANKS.COM 
