Table of Contents
Introduction
Overview of Rainwater Harvesting in the U.S.
Above-Ground Tanks
3.1. Features and Construction
3.2. Advantages
3.3. Disadvantages
Underground Tanks
4.1. Features and Construction
4.2. Advantages
4.3. Disadvantages
Cost Considerations
Installation Complexity and Requirements
Maintenance and Longevity
Regulatory Factors
Making the Right Choice for Your Home
Conclusion
References
Rainwater harvesting has gained significant traction across the United States as a practical strategy to conserve water, reduce utility bills, and increase a home’s overall resilience. At the heart of any rainwater harvesting system is the storage tank, which collects and holds the water that falls onto your roof or other catchment surface.
When choosing between above-ground or underground storage tanks, factors like budget, space constraints, local climate, aesthetics, and regulatory requirements play a major role. This blog will guide you through these considerations so you can make an informed decision that aligns with your goals and circumstances.
In many parts of the country—particularly drought-prone regions—rainwater harvesting can offer a reliable supplementary water supply. States like Texas, Arizona, Colorado, and California have developed specific guidelines and incentives to encourage responsible water reuse. As more American homeowners seek sustainable solutions, above-ground and underground tanks have emerged as the two primary storage options for residential rainwater harvesting systems.
3. Above-Ground Tanks
3.1. Features and Construction
Above-ground tanks, also known as surface tanks, are typically made from materials such as:
High-density polyethylene (HDPE)
Fiberglass
Corrugated steel
Flexible bladder tanks
These tanks are installed on a stable, level surface—often concrete or a well-prepared gravel base—next to the house or another accessible location on the property.
3.2. Advantages
Lower Installation Costs
Above-ground installations are generally simpler and less labor-intensive. You often just need a suitable level pad, basic plumbing connections, and possibly a pump if you plan to distribute water throughout the home.
Easy Inspection and Maintenance
Since the tank is fully visible, identifying leaks or structural issues is straightforward. Maintenance tasks like cleaning and repairing can be performed with fewer specialized tools.
Shorter Installation Time
With no excavation required, most above-ground tanks can be installed and operational within a few days.
Adaptability
If you decide to move or replace your tank, it is relatively easy to disassemble and relocate an above-ground system.
3.3. Disadvantages
Aesthetic Concerns
Large tanks can be visually intrusive, which might not align with neighborhood aesthetics or homeowners’ association (HOA) guidelines.
Temperature Fluctuations
Above-ground tanks are more susceptible to extreme heat or cold. This can influence water temperature, promote algae growth (especially if the tank is translucent or lightly colored), or lead to freezing in colder climates.
Space Requirements
Depending on capacity, these tanks can occupy substantial yard space, potentially limiting landscape design.
Vulnerability to Weather and UV Radiation
Tanks exposed to direct sunlight may degrade faster, particularly if not properly UV-stabilized. Severe weather events, such as hurricanes or tornadoes, can also dislodge or damage above-ground tanks.
4. Underground Tanks
4.1. Features and Construction
Underground rainwater storage tanks are typically constructed from:
Concrete
Polyethylene or polypropylene (reinforced for underground use)
Fiberglass
These tanks are installed below the surface of the ground, requiring excavation and careful backfill. The location and depth depend on factors like local frost lines, soil conditions, and the capacity required.
4.2. Advantages
Space-Saving and Aesthetic Appeal
Underground tanks are hidden from view, leaving your yard open for landscaping or other uses. This can be especially advantageous in smaller or highly regulated neighborhoods.
Stable Water Temperature
Being below ground level helps insulate the tank, reducing the risk of freezing in winter or overheating in summer. This temperature stability can also deter algae growth.
Protection from the Elements
Underground placement shelters the tank from UV rays, weather extremes, and physical damage from storms or debris.
4.3. Disadvantages
Higher Installation Costs
Excavation, specialized materials (e.g., reinforced tanks), and professional labor can make underground tanks significantly more expensive to install than above-ground systems.
Complex Maintenance and Inspection
Accessing an underground tank often requires lifting heavy covers, entering confined spaces, or using specialized equipment. This can complicate routine inspections or repairs.
Potential for Leakage or Groundwater Contamination
If installed incorrectly or if soil conditions are poor, underground tanks can shift or crack, allowing groundwater to seep in or stored water to leak out.
Local Soil and Water Table Considerations
High water tables, rocky terrain, or unstable soil can make underground installations impractical or cost-prohibitive.
5. Cost Considerations
Above-Ground Tanks
Initial Cost: Typically lower, especially for smaller tanks. A simple 300- to 500-gallon poly tank could cost anywhere from $200 to $1,000, excluding installation.
Installation: Generally minimal site prep (like leveling ground or pouring a small concrete pad) plus plumbing.
Underground Tanks
Initial Cost: Can range widely, from $1,000 for smaller pre-cast concrete tanks to tens of thousands of dollars for large-capacity reinforced systems.
Installation: Excavation, backfill, potential use of heavy machinery, and specialized labor all add to the cost.
Other factors include:
Pumps and Filtration for Your Plumbing Needs
Both systems often require a pump to distribute water, especially when considering your plumbing needs for household fixtures or irrigation with sufficient pressure. Filtration needs vary based on intended water use (potable vs. non-potable), ensuring your plumbing needs are met efficiently and safely.
Permits and Inspections: Depending on local regulations, you may need a permit for the tank and for integrating the harvested water into household plumbing.
6. Installation Complexity and Requirements
Permits and Zoning: Some municipalities classify large water storage tanks as structures, requiring permits. Underground tanks may trigger additional inspections due to excavation and soil disturbance.
Soil Testing: Particularly for underground tanks, soil composition and stability must be assessed to ensure proper installation.
Frost Line Depth: In colder regions, underground tanks must be placed below the frost line to avoid damage from freezing and thawing.
Access to Electricity and Plumbing Lines: Pumps require power, and you may need to run piping from the gutter system to the tank and from the tank to the points of use.
7. Maintenance and Longevity
Above-Ground Tanks
Inspection Frequency: Every few months, or after major storms, to check for leaks, algae growth, or UV damage.
Cleaning: Draining and cleaning the interior can be done relatively easily.
Lifespan: Depending on material and exposure, well-maintained above-ground tanks can last 15–25 years or more.
Underground Tanks
Inspection Frequency: Annual or semi-annual checks are recommended, but these can be more involved.
Cleaning: May require pumping out the tank and professional cleaning or inspection services.
Lifespan: Quality materials and professional installation can yield a lifespan of 20–30 years or more, especially for concrete tanks.
8. Regulatory Factors
Rainwater harvesting regulations differ widely across the United States. Key considerations include:
State-Level Laws: Some states encourage rainwater harvesting with rebates or tax incentives (e.g., Texas, Arizona). Others have more stringent guidelines (e.g., Colorado historically limited catchment but has since relaxed some restrictions).
Local Building Codes: Zoning regulations, setback requirements, and plumbing codes may dictate where tanks can be placed and how they must be installed.
Health and Safety Codes: If you plan to use harvested rainwater for potable purposes, advanced filtration and disinfection systems may be required. Check the Uniform Plumbing Code (UPC) and local amendments.
For the most accurate, up-to-date information, consult your city or county’s water department, planning office, or local extension services.
9. Making the Right Choice for Your Home
The decision between an above-ground or underground rainwater storage tank ultimately depends on:
Budget: Consider not only the tank cost but also installation, maintenance, and potential future repairs.
Property Constraints: Evaluate available space, soil conditions, and how visible you’re willing for your tank to be.
Climate: Harsh winters or extremely hot summers may steer you toward one option.
Personal Aesthetics: Underground tanks preserve the look of your landscape, while above-ground tanks are simpler and cheaper.
Long-Term Goals: If you plan to expand your system later, a modular above-ground system may be easier to upgrade, while a larger underground cistern might be preferable for significant water storage from the outset.
10. Conclusion
Rainwater harvesting is a versatile, eco-friendly solution that can help reduce water bills, conserve resources, and contribute to household self-sufficiency. Whether you opt for an above-ground or underground tank, careful planning and adherence to local regulations will ensure you reap the full benefits.
Above-Ground Tanks are cost-effective, straightforward to install, and easy to maintain. They suit those with tighter budgets or those who prioritize accessibility.
Underground Tanks offer superior aesthetics, stable water temperatures, and protection from the elements but require a larger investment, more complex installation, and specialized maintenance.
By weighing these factors—along with your climate, local regulations, and personal preferences—you can select the storage solution that meets both your current and future water needs.
11. References
American Rainwater Catchment Systems Association (ARCSA). (n.d.). Rainwater Catchment Best Practices. https://www.arcsa.org/
City of Austin. (n.d.). Rainwater Harvesting Rebates and Resources. https://www.austintexas.gov/department/water
Colorado General Assembly. (2016). Rain Barrel Legislation (HB16-1005). https://leg.colorado.gov/
IAPMO. (2018). Uniform Plumbing Code. https://www.iapmo.org/
Texas Water Development Board. (2005). The Texas Manual on Rainwater Harvesting. https://www.twdb.texas.gov/
U.S. Green Building Council. (n.d.). LEED Certification and Water Efficiency Credits. https://www.usgbc.org/leed
Disclaimer: Rainwater harvesting laws and building codes vary by state and municipality. Always consult local regulations and consider hiring a professional for installation to ensure compliance and safety.