Above Ground vs Underground Water Storage Tanks

Posted by
John Woodard on January 27, 2023

Water tanks are a popular solution for saving on your water bill, but knowing what type of tank to purchase can be tricky. While underground tanks are more expensive than above-ground tanks, they do possess many benefits that are well worth the added cost. Below you can find information on what a water storage tank is, the differences between underground and above-ground tanks, and the advantages and disadvantages of both tank types.

What is a water storage tank?

A water storage tank is a container connected to a gutter system used to collect rainwater. Rainwater harvesting is a common practice for homeowners who live in drought-prone regions or who want to save money on their water bill. Collected water can be used for gardening, washing cars, watering a lawn, and other outdoor applications. If a water filtration system is connected to your water tank, rainwater can be used for potable applications inside a home.

Rainwater harvesting can help save money on your water bill, keep your plants healthy, and benefit the environment. If you use water regularly for outdoor applications, collecting rainwater can help you save dozens of gallons of water per month. Since rainwater does not contain chemicals added in city water treatment, using rainwater on your plants can be beneficial to their health. Another way rainwater harvesting can benefit the environment is by reducing soil erosion. Runoff from a rooftop pools on the ground underneath, displacing soil and causing soil aggregates to break. If water deviates to a storage tank instead of the soil, soil erosion can be avoided, and you will get the added benefit of useable water.

Learn more: What Is a Rain Barrel and How Does It Work?

What are the differences between above ground and underground water storage tanks?

While both above ground and underground water storage tanks are used for the same thing, they come with many differences in their installation, maintenance, and cost.


Installing an above-ground water storage tank

Installing an above-ground tank is much simpler than installing an underground one. The most difficult part of installing an above-ground tank is placing it in the correct location. Depending on the size of the tank, this task could be easy or somewhat difficult. You will want to install your tank next to the downspout that collects the most rainwater. Once in the correct location, attach the inlet of the tank to a downspout connector, and the water that runs down your downspout will deviate into the tank.

Installing an underground water storage tank

Underground water storage tanks require proper planning before installation. An appropriate-sized hole needs to be excavated and filled in once the tank is in place. In addition, underground plumbing needs to be attached to the tank to properly bring rainwater into the tank. You can expect to pay around $3000 in labor costs for your underground storage tank. The price of installation will vary depending on the size of your tank and variables such as ground composition and tank location that may make installation more difficult.

truck lifting storage tank


Maintaining an above-ground water storage tank

Maintaining an above-ground tank is easier than maintaining an underground one, but you may need to perform maintenance more often. Because above-ground tanks are exposed to the elements, cracks are more likely to form. In addition, you are more likely to notice cracks on an above-ground tank than an underground one. You will only notice problems with an underground tank when it stops functioning.

To maintain your above-ground tank, you will want to ensure that it does not store water when the temperature drops below freezing. If you wish to store rainwater during the winter months, you will need to insulate your tank. Insulation for water tanks includes spray-on insulation, injected insulation, and an external wrap or blanket. Water stored inside the tank during freezing temperatures will freeze and expand, forming cracks along the tank’s exterior. To fix a crack in your tank, you can use either a fiberglass sheet, epoxy, or putty. Before applying any of these options, clean the area of the crack and its surroundings to ensure bacteria is not trapped inside.

How to clean your above-ground storage tank

Once every six months, your above-ground water storage tank needs to be emptied and cleaned. Follow these steps to clean your above-ground water storage tank:

  1. Leave a small amount of water at the bottom of the tank to aid you while cleaning.
  2. Use a brush to scrub around the inside of the tank.
  3. Rinse the tank with filtered water and allow it to dry.
  4. Add enough chlorine bleach to the tank so that it maintains a level of 50 parts per million (ppm) or higher once the tank is filled with water.
  5. Allow this solution to sit for 24 hours. Ensure that no one accesses the tank during this time.
  6. Drain the tank. Ensure that you do not drain the chlorine solution into vegetation or any area where plant or animal life will be affected.
  7. Rinse the tank thoroughly. If any chlorine is left over, it can harm plants if you use stored rainwater for gardening.
  8. Allow the tank to dry.
  9. Reconnect the tank to the downspout.

blue water storage tank

Maintaining an underground water storage tank

Maintaining an underground water storage tank is not as consistent of a task as maintaining an above-ground tank, but underground tanks are more difficult. Since the tank is underground, you do not have to worry about weather affecting the water’s temperature or the exterior of the tank. Because above-ground tanks are exposed to the elements and underground tanks are not, you need to clean underground tanks much less often than above-ground tanks. Underground tanks should be cleaned once about every five years. If you notice algae growth or any contamination in your water, you need to clean your tank right away.

Cleaning an underground water storage tank is the same process listed above as cleaning an above-ground tank. Note that when draining an underground tank, you will want to bypass the septic system when draining the chlorine solution.

If you believe your underground tank contains cracks or other structural damage, contact a professional to inspect your tank. Catching a problem early with your tank can save you from headaches later on, as cracks can expand quickly and become more expensive to repair.


Cost of an above-ground water storage tank

The following are the costs of above-ground tanks in a variety of sizes:

Installation for a 1000-gallon above-ground storage tank averages around $1700. Most of this cost stems from the delivery fee because large tanks are difficult to ship.

Cost of an underground water storage tank

A Norwesco 1175 Gallon Low Profile Tank costs $1824. Installation for an underground tank typically costs around $3000, putting an estimated cost of this harvesting system at just below $5000. The cost of installation depends on tank size and how easy the tank is to install, taking factors such as ground composition and tank location into consideration. Installing an underground tank is not a DIY job, so you will want to hire a professional.

above ground rain storage tank

Pros and cons of water storage tanks

While both above ground and underground water tanks are excellent for rainwater harvesting, both have advantages over the other in certain situations.

Advantages of above-ground water tanks

  • Above-ground tanks are much easier and less expensive to install than underground ones. Since no digging or underground plumbing is needed, installation is much less costly than underground tanks that require a professional.
  • If you decide to move homes, you can easily relocate an above-ground tank. Above-ground tanks do not need to be connected to a gas line or sewage system like an underground tank. Instead, they must be connected to a downspout, so they can also be easily relocatable within a yard.

Disadvantages of above-ground water tanks

  • Above-ground water tanks are susceptible to damage when exposed to the elements. If water freezes inside the tank, it will expand as it freezes and crack the tank’s exterior. If the climate in your area is prone to freezing, you will need to either insulate the tank in the winter or empty and avoid using it during the cold months altogether. Adding insulation to an above-ground tank can be costly, taking away some of the benefits of its relative inexpensiveness compared to underground tanks.
  • Above-ground tanks can be difficult to make aesthetically pleasing. While above-ground tanks are often sold in natural colors to blend into the environment, hiding a tank that stores hundreds of gallons of water is practically impossible.
  • Theft and vandalism are problems associated with above-ground tanks. Because they are so hard to hide and are valuable, above-ground tanks can be targets for burglars. During the California drought, thieves drove up to homes and stole water from storage tanks. Some homeowners have even had their entire tank stolen. While someone stealing your storage tank may seem unlikely, it has happened and cannot happen with an underground tank.

Advantages of underground water tanks

  • Underground tanks are more aesthetically pleasing than above-ground tanks. Underground tanks are completely hidden, so they are invisible to an outside observer. Homeowners with an underground tank do not have to worry about incorporating a storage tank into the design of their outdoor space.
  • Underground tanks maintain a consistent temperature throughout all four seasons. The ground above the tank insulates it from extreme hot and cold temperatures. This prevents the water from freezing and cracking the exterior of the tank.
  • While they are more expensive to install than above-ground tanks, underground tanks can be made from repurposed septic tanks. Septic tanks that are abandoned or no longer needed can be turned into rainwater storage tanks. New plumbing would be needed for the tank’s new purpose, but overall installation costs would be much less than for a brand new tank. A tank should always be inspected for quality before being repurposed.
  • Underground tanks save space in your yard. They are much preferable for homes with small lawns or lack of suitable locations for an above-ground tank.

Disadvantages of underground water tanks

  • Installing an underground tank costs more than installing an above-ground tank. The added expenses of digging, plumbing, and professional installation make underground tanks pricier than their above-ground counterparts.
  • Maintenance is more difficult to perform and more expensive in underground tanks. While having a storage tank underground protects it from the elements, accessing an underground tank takes much more effort than an above-ground tank. While underground tanks may require less maintenance than above-ground tanks, performing it on underground tanks takes longer because of the steps needed to access them.


If you have any questions about rainwater harvesting, please do not hesitate to contact us.

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