Storage Systems

Wahaso Storage Systems

One of the key decisions in designing a water harvesting system is to determine the type and volume of the storage.

Storage Systems & Options

Select a storage system that is too small and the opportunity to capture and store water between uses is diminished, with excess rainwater is being directed to the city storm system instead of being retained for flushing toilets or irrigating landscaping. Select a storage system that is too large, and the result can be expensive wasted capacity that is not needed. Wahaso offers a free analysis that not only looks at the incoming supply of harvested water, but also at the potential demands such as toilet flushing, irrigation and cooling tower make-up. This analysis allows us to determine the optimum volume of storage and we work with the client to determine the best type of storage to fit the project. Each storage option advantages and disadvantages.

Pre-Cast Concrete

Concrete isa strong, versatile and space-efficient method of below-grade storage. Concrete cisterns can be poured in place, but that process can be expensive and time consuming, especially at a busy construction site.


  • Easy to install and uses any on-site material for backfill.
  • The modular nature allows for a flexible footprint and depth.
  • Reinforced concrete has high strength under load-bearing surfaces.


  • Requires heavy equipment to lift modules for installation.
  • Requires water proofing (liners and sealant).
Another option is prefabricated concrete cisterns. Wahaso partners with Oldcastle Precast to offer the Storm Capture® system comprised modular pre-cast concrete units.

Modular Polypropylene System

Modular polypropylene systems for below-grade storage offer versatility at a competitive price. Wahaso partner, Atlantis®, provides their Rain Tank system comprised of polypropylene plates that are easily assembled on site.
The tank is wrapped in a geotextile filter medium and stabilized with compacted washed sand. For water retention and reuse, the excavation is lined with a 300 ml poly liner that contains the water in the cistern.


  • Cistern can be assembled on-site, reducing the cost of shipping and eliminating the need to use a crane for install.
  • The plates are made from recycled polypropylene, which is not only sustainable but meets LEED requirements for Materials and Resources.
  • Beneficial micro-organisms in the sand layer and biofilm that builds on the plates help to digest organic material and help to keep the tank clean.
  • While the installation of the tank does not require a crane, it does require man-hours to assemble the modules, place them and wrap the cistern with the waterproof lining.
  • Installation may be difficult in areas with a high water table.



Fiberglass has long been used for below-grade storage. It comes in many standard sizes from 1,000 to 40,000 gallons. Should more storage be required, multiple tanks can be connected, and the water equalized between them.

Wahaso partners with Containment Solutions, Inc., a division of NOV Fiberglass Systems, for a trusted name in storage tanks.


  • The cost of the heavy lifting equipment is lower than that used for concrete, as the fiberglass is lighter weight.
  • Fiberglass cisterns have been used for decades and are a familiar storage method to many clients.


  • Storage footprint is restricted by the set dimensions of the cylindrical tanks.
  • Installation requires anchoring and specific backfill so as not to damage the fiberglass.

Corrugated Steel Tanks

Corrugated steel tanks provide the iconic look of water harvesting. The above-grade structures are a signal that the property owner is employing sustainable water practices.


  • Attractive structure that advertises the owner’s commitment to sustainability.
  • Long-lasting steel tanks are made in the USA.


  • Requires certified installer to erect the tank on site.
  • Requires custom concrete base pad.
Wahaso partners with Water Storage Tanks, the manufacturer of Corgal tanks, to provide steel tanks as small as 600 gallons and as large as 500,000 gallons. Reinforced PVC liners keep each tank water tight.

Polyethylene Tanks

Polyethylene and high-density polyethylene tanks are a solid option for above-grade storage located inside or outside the building. If located outside the building, Wahaso recommends using a tank with UV inhibitors. These types of tanks are typically best suited for projects with a small storage volume or a small budget. If larger volumes are required, the tanks can be joined together and the water equalized between them.


  • Poly tanks can be a cost-effective solution for small storage systems that need to be located inside a building, or outside, above-grade.
  • Many shapes and sizes are available, allowing for flexibility if there are any space limitations.
  • No on-site assembly is required.


  • Utilitarian in appearance and therefore, not an ideal choice for projects where the tank is visible to the public.
  • Being a petroleum-based material, polyethylene cost can be subject to price swings.

Since 2004

Wahaso Mission

Our mission at Wahaso is to help municipalities and commercial property owners reduce the impact of their buildings on the environment through innovative and sustainable water practices.