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Rainwater Collection Tanks

Though they could easily be described as a big container for water, rainwater harvesting tanks are much more complicated than that. A lot goes into which tank is right for you and how to properly install and maintain that tank.

Rainwater collection continues to grow in popularity, leading some curious people to ask more in-depth questions about the process. One of the most common interests for people thinking about installing a rainwater harvesting system is where those big tanks go and how they work. This breakdown of rain harvesting tanks, their size, installation, and safety will give anyone thinking about installing one of these systems peace of mind about their off-grid future.

How Does Rainwater Harvesting Work?

Although the results are incredible, the process is easier than one may think.

  1. Rain falls on the roof and rolls down to the gutters.
  2. The gutter leads to a conveyance system transporting rainwater to the tanks.
  3. Before reaching the tanks, the water goes through a pre-filtration system that removes large contaminants like sticks and leaves.
  4. The water collects in the tanks until it is ready to be used.
  5. When needed, the water is pumped to the house through a multi-step filtration process which delivers pure, soft water on demand.

Above Ground vs. Inground

If you are in the planning stages of installing a rainwater harvesting system, one of your most significant decisions is whether your holding tanks will be above ground, below ground, or somewhere in between. Of course, each option has its advantages and disadvantages, so it all depends on what's best for your household.

Above Ground

Having your storage tanks above ground gives you more options than in-ground tanks, and it also reduces the installation costs since there is significantly less excavating needed. However, many people don't like above-ground tanks because they are not aesthetically appealing. Some homeowners like the way the tanks look on their property, while others choose to hide above-ground tanks behind landscaping. These tanks are also more susceptible to the elements and natural disasters than their in-ground counterparts.

Partially Buried

This type of installation softens many of the disadvantages of above-ground tanks, making them easier to hide and more protected from natural disasters. A traditionally above-ground tank is buried a quarter to halfway into the ground in this method.


This option has a few drawbacks, like the cost of excavation, a larger footprint, and the load-bearing capacity of some tank materials. The cost of excavation can be even higher if you run into a large boulder that needs to be removed, so a higher budget is required for surprises. What makes this an attractive and common option is that your tanks are protected underground, they are out of sight, and you can use the space on your property above the tanks.

Types of Tanks

Above or Partial Polyethylene

These budget-friendly options are a favorite because they come in many shapes and sizes and can be connected by a crossover pipe as long as the tanks are level. These tanks don't have the highest capacity, but the fact they can be connected gives a little more assurance. For example, three 2,500 gallon tanks will connect to hold 7,500 gallons of rainwater.

In-Ground Polyethylene

These tanks have all the same features as above-ground polyethylene tanks, but they are ribbed to provide load-bearing support.


Fiberglass has a high load-bearing capacity, so these tanks are often used in commercial and industrial settings. They would also be perfect for a farmstead with large machinery moving back and forth all day. These tanks can be installed under or above-ground and can hold anywhere from 1,000 to 50,000 gallons.


These tanks are great for high-capacity above-ground storage. They are solid and fire-proof, meaning that they can withstand nearly any natural disaster. In addition, bolted steel tanks can be built in almost any size to hold anywhere from a few thousand to a few million gallons.

Wood Tanks

Wood tanks are aesthetically appealing, making them great for above-ground storage, but size constraints and materials make them better for a backup reserve than your primary water source. Of course, they have lining on the inside to hold water and prevent direct contact with the wood.

Water Bladder

This above-ground option is usually used in commercial settings for temporary water storage. They are made from a strong coated fabric and can hold 100 to 300,000 gallons of water depending on their size.

Modular Storage

This commercial application is a combination of plastic-lined crates that store water underground. They offer unlimited options for size and capacity but require a footprint that is not often available in a residential setting.

Here is more information about the different types of tanks.

Capacity Concerns

With so many different options, you're likely wondering how much capacity you'll need and what happens if you ever run out of water. While it's impossible to know for sure, we do everything we possibly can to ensure that you will never run out of water. During the planning phase of the process, we take vital metrics that will help us choose the suitable storage capacity for you, including 100 years of rainfall data in your area and how many gallons of water the homeowner can expect to use each month of the year. In the case of severe drought, our storage system will automatically switch over to another water source until the tanks are refilled, and all of our tanks come with a fill-port, so an outside water source can be used to refill the tanks.

Are Water Tanks Safe?

The CDC does not recommend drinking rainwater that is not properly stored, which may make some people wary of water harvesting, but it is actually one of the safest ways to get your drinking water.

Good Vs. Bad Bacteria

There is no way around there being bacteria in your rainwater. It can come in contact with all sorts of stuff before it enters the tank, but there are also good bacteria already living in your tank. The good bacteria is called biofilm, and it is a naturally occurring layer of bacteria that sits on the bottom of a properly designed rainwater harvesting tank. Biofilm acts as a natural filter for the water, continuously cleaning out unwanted particles.

There are harmful bacteria that occasionally get into rainwater too, but that is removed by a combination of carbon filtering and UV light before it ever reaches your faucet.

Mold and Algae

In poorly designed above-ground tanks, you run the risk of mold or algae growing in the tank. Our specially designed tanks block UV rays to prevent organic growth.


If the wrong materials are used for a rainwater storage tank, toxins can leach into the water, making your water dangerous to ingest. A rainwater harvesting tank must be NSF-61 certified to ensure nothing will leach into your water.

Don't Tank Your Project

Though they could easily be described as a big container for water, rainwater harvesting tanks are much more complicated than that. A lot goes into which tank is right for you and how to properly install and maintain that tank. If this sounds intimidating, don't worry; contact us, and we can take you through the step-by-step process to ensure that you are getting the right material, the right size, and the proper placement of your rainwater harvesting tank.

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