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A Better Way to Contain the Rain

Rainstore3 is a modular, stackable, underground water containment system. This innovative solution was designed by a landscape architect for subsurface detention basins, retention/harvesting systems, water/rain gardens, green roofs, and sports field drainage. 

Featuring a lifetime warranty, the first Rainstore3 installation was in 1999 and all existing installations are still going strong.

Rainstore3 Advantages

  • Modular and Stackable
  • 94% Void Space with No Gravel Fill
  • Exceeds H-20 Loading
  • No Assembly Required
  • 100% Recycled Polypropylene (PP) Plastic
  • LEED Certified
  • Lifetime Warranty


  • Underground Detention Basin
  • Retention/Harvesting Systems
  • Water/Rain Gardens
  • Green Roofs
  • Sports Field Drainage
  • Run-Off Capture and Reuse
  • Downspout Catch Basins
  • Liquid Batter Storage

Incredibly Strong

Rainstore3 is strong enough to support almost any project, including parking areas, fire lanes, and even small buildings. Use our cost estimator to learn more about the configuration and costs.

Featured Case Study

South Battery Park

New York City chose Rainstore3 for its Battery Park enhancement project to capture overflow stormwater and protect the area from flooding.

Read more


"The Rainstore3 system is being used as part of the South Battery Park Resiliency Project. The goal of the project is to protect Lower Manhattan from storms such as Hurrican Sandy. Specifically, the Rainstore3 system is being used as a water retention and greywater system which is going to feed a new building which is going up in Battery Park ... the system was even easier to install than we thought it was going to be!"

- On-site Supervisor, Battery Park Project, NYC

Technical Information

Design Details
Data Sheets
White Papers
Specifications and Instructions
Product Sizes and Information
Estimate Calculator

Rainstore3 Frequently Asked Questions

What is Rainstore3?

Rainstore3 is a modular stackable underground water/liquid containment system. It is installed subsurface to be used as detention basins and retention harvesting systems. Made from 100% recycled plastic, units come preassembled for easy drop-in-installation.

What are the common applications for Rainstore3?

Rainstore3 is a solution for stormwater retention and detention as well as other applications requiring liquid storage. Water will percolate through the ground or covering and can either run through Rainstrore3 at a controlled rate or be stored for later use. Common applications include:

  • Underground Detention Basin
  • Retention/Harvesting Systems
  • Water/Rain Gardens
  • Green Roofs
  • Sports Field Drainage
  • Downspout Catch Basins
  • Utility Liquid Battery Storage

What is the cost of Rainstore3?

Please see our Rainstore3 Estimator for product cost.

What are the main advantages of Rainstore3?

Rainstore3, arrives pre-assembled, for easy installation. It is modular and stackable so can be installed in a wide range of depths, maximizing the capacity of water storage.

What is stormwater management?

Stormwater management is anything designed to mitigate the adverse effects of stormwater such as flooding, mud, rutting, pooling and general lack of drainage. All Invisible Structures products are designed to address these issues.

What is an underground detention system?

Underground detention systems include any structure or vessel designed to store rainwater or other liquid beneath the surface of the ground. A primary function of the vessel is stormwater management. Rainwater can be captured and fed back into the Earth to replenish groundwater or collected and harvested for future use. Storing water underground provides additional security as well. Examples of underground detention systems include arched chambers and plastic modular systems such as Rainstore3.

What are rainwater collection systems?

Rainwater Collection Systems include any vessel, tank or other basin that is designed to collect and store excess rainwater. Examples of these are barrels, concrete storage tanks, arched chambers, detention basins and plastic modular systems – such as Rainstore3. Reasons to collect excess stormwater vary from flood prevention to harvesting for the purpose of reuse. The efficacy of these systems differ based on size and design.


Rain barrels and concrete storage tanks are limited in their capacity because of their impervious walls, whereas arched chambers, detention basins, and plastic modular systems have unlimited capacity. Arched chambers and plastic modular systems have the advantage of storing water underground, allowing for usable space such as parking lots or green spaces on top.


Only Rainstore3 is strong enough to support the weight of structures such as a parking garage or small building.

Should I use a rainwater collection system?

There are several reasons to use a rainwater collection system. In areas with heavy rainfall where drainage is an issue, these systems can help mitigate the problems caused by flooding. All climates, including arid, can benefit by capturing rainfall and harvesting the water for reuse. Reusing water can save money and provide environmental benefits.


Another advantage of underground rainwater collection systems, not designed for harvesting, is that they can replenish the groundwater. Water shortages and the decrease in our ground water are among the planet’s biggest environmental concerns today.

What types of rainwater collection systems are there?

There are several different types of Rainwater Collection systems. These include rain barrels, concrete storage tanks, arch chambers, milkcrate systems, and other plastic modular systems – such as Rainstore3. These different systems vary in size, cost, ease of installation and water storage/void capacity.


Rain barrels are the least expensive and do not require professional installation. Their capacity is limited by the size of the barrel. Concrete storage tanks are moderate in cost, also limited by their tank size, and require professional installation.


Arch chambers require a sizable installation area and a considerable amount of gravel fill which can be expensive. The void space is 40 – 50%. Milkcrate systems are mid-range in price but require complex assembly, which can add to the cost of labor. Their capacity is unlimited.


Modular plastic storage systems tend to be the highest initial cost but installation is relatively simple. Their capacity is also unlimited. Another benefit to plastic modular systems is the high void capacity and strength – Rainstore3 exceeds H-20 loading.

What is the weight capacity of Rainstore3?

Rainstore3 exceeds H-20 loading allowing it to support vehicular traffic, lightweight buildings or greenspace. Please see our H-20/Hs-20 Guide for more information.

How much water can Rainstore3 hold?

Rainstore3 is 94% void space. A single unit holds almost 25 gallons, which means each cubic meter is capable of holding up to 250 gallons.

How are rainwater collection systems used?

Rainwater collection systems are used for either water detention or water harvesting. Either method is an effective way to control stormwater for flood prevention. For reuse, water harvesting is required from an impervious vessel or storage basin. Harvested water can be used as gray water, for agricultural purposes or can be purified and used as potable water.


Water detention basins allow water to seep back into the ground recharging the ground water. The depletion of ground water has become one of the biggest environmental concerns our planet is facing.


All collection systems require some minimal maintenance in order to maintain optimal functionality.

How much rainwater can a rainwater collection system collect?

The amount of rainwater which can be collected varies by the type and size of the collection system used. Rain barrels typically hold 50 – 55 gallons per barrel. A rainfall of ½” on a 1,000 sq. ft. roof will fill one barrel. Concrete and plastic storage tanks range in size from 250 gallons to 15,000 gallons.


Arch chambers, milkcrate and plastic modular systems are only limited by the length, width and depth of the area as well as the void space of the system. For example, arch chambers provide only 40 – 50% space for water whereas Rainstore3 provides 96%. Therefore, each 1 meter piece of Rainstore3 holds up to 25 gallons, even though it’s only 4” high. At the maximum depth of almost 8’, 24 units of stacked Rainstore3 can hold almost 600 gallons of water in a single stack.

What is the installation process for Rainstore3?

Rainstore3 comes in preassembled custom height stacks that can be unloaded and dropped directly into the job site. Installation is fast and easy. For additional details please see the Rainstore3 Installation Guide.

How are the inlet/outlet pipes attached to Rainstore3?

Inlet and outlet pipes can be attached to Rainstore3 by forming a “boot” with the fabric or liner and securing it with a hose clamp.

How much cover is required over the Rainstore3 system?

A minimum of 12” of compacted road base and a geogrid layer is required above the Rainstore3 chambers.

What keeps the soil from entering the cells?

Rainstore3 is wrapped in a geotextile fabric or PVC liner so soil and vegetation are unable to penetrate the chamber.

Can Rainstore3 be inspected after it is installed?

Adding maintenance ports during installation allows Rainstore3 to be inspected after the installation is complete. Please see the Rainstore3 Maintenance Guide for Details.

Is silt buildup an issue?

Silt buildup can be prevented by using proper pre-filtration, such as catch basins or sediment filters. Using Rainstore3 in conjunction with Grasspave2 or Gravelpave2 can eliminate the need for any filtration systems as the water would be filtered naturally through bioremediation.

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