Rainwater harvesting has become increasingly popular across the United States for a variety of reasons: water conservation, cost savings on water bills, disaster preparedness, and environmental stewardship. Key to a successful rainwater harvesting system is the storage tank, which holds the rainwater for later use in irrigation, toilet flushing, laundry, or—if properly filtered and treated—potable water.
Choosing the right type of tank is a pivotal decision that influences cost, space requirements, maintenance, and overall system performance. The two most common options for residential properties are above-ground and underground rainwater storage tanks.
2. Why Rainwater Harvesting Matters
Water Conservation: By capturing precipitation, you reduce reliance on municipal water supplies and alleviate stress on local aquifers.
Cost Savings: Depending on local water rates and how much of your household’s water needs can be met by harvested rain, you can substantially lower monthly utility bills.
Stormwater Management: Harvesting rainwater decreases runoff, reducing the load on local stormwater systems and mitigating flooding risks.
Environmental Benefits: Using non-chlorinated, naturally soft rainwater for irrigation or other household tasks can be healthier for plants and helps conserve treated municipal water for essential potable use.
In the U.S., different regions face unique climate and regulatory conditions that can make above-ground or underground tanks more suitable. Let’s explore each system in detail.
3. Above-Ground Rainwater Storage Tanks
3.1. Design and Materials
Above-ground tanks are typically constructed from materials like polyethylene (plastic), metal (steel or aluminum), or even fiberglass. They are installed on a stable, level surface—often a concrete pad or a compacted gravel bed. The capacity can range from modest 50–200-gallon barrels to large 5,000–10,000-gallon or more cisterns.
Common designs include:
Barrel Tanks: Common in small-scale residential projects.
Vertical Cylindrical Tanks: Larger-capacity cylindrical units placed in plain view.
Slimline Tanks: Designed for narrow spaces, particularly in urban settings.
3.2. Advantages
Lower Upfront Costs: Above-ground tanks typically cost less to purchase and install, as they do not require excavation.
Easier Installation: Generally simpler to set up; in many cases, they can be installed without hiring specialized contractors or using heavy equipment.
Accessibility for Maintenance: Owners can quickly inspect the tank, check for leaks, or clean the interior through accessible hatches and openings.
Portability: Some above-ground tanks can be relocated if you move or if your landscaping changes.
3.3. Disadvantages
Aesthetics: Large plastic or metal tanks can be visually unappealing. While some homeowners embrace a utilitarian look, others find them to be an eyesore.
Temperature Fluctuations: Exposure to sunlight and ambient temperatures can raise or lower the water temperature dramatically, promoting algal growth and other water quality issues if not properly shielded or insulated.
Limited Protection from External Elements: Extreme weather, harsh UV rays, or impacts from debris can damage or degrade above-ground tanks more quickly than underground ones.
4. Underground Rainwater Storage Tanks
4.1. Design and Materials
Underground tanks are typically made of concrete, fiberglass, or polyethylene reinforced for subterranean use. They are installed below the frost line in cold regions or at a sufficient depth to protect the structural integrity of the tank from soil pressure and external impacts.
Key design considerations:
Excavation: A hole large enough to accommodate the tank plus backfill must be dug, often requiring professional machinery.
Structural Integrity: Underground tanks must be designed to withstand soil load, especially in areas with high water tables or heavy clay soils.
4.2. Advantages
Aesthetics: Because they’re out of sight, underground tanks preserve the visual appeal of your property—no large container occupying yard space.
Temperature Stability: Underground tanks are less susceptible to temperature swings, which can help maintain better water quality over time.
Protected from External Damage: Being buried insulates the tank from physical damage due to weather, falling debris, and UV exposure.
4.3. Disadvantages
Higher Installation Costs: Excavation and site preparation can be expensive, particularly in rocky or sloped terrains.
Complex Maintenance and Repair: Access is more difficult; locating and fixing leaks or performing internal cleaning often requires specialized equipment or professional services.
Potential Water Table Issues: In areas with high groundwater levels, hydrostatic pressure can damage an underground tank or cause it to “float” if not properly anchored.
5. Comparative Factors
5.1. Cost and Installation
Above-Ground: Typically cheaper and faster to install. A 1,000-gallon above-ground polyethylene tank can cost between $700 and $1,500, plus minimal site preparation.
Underground: Can cost substantially more due to excavation, site engineering, and the need for robust tank construction. Costs for a 1,000-gallon underground system might start around $2,000–$4,000, excluding excavation fees, which can add significantly to the total.
Tip: Always obtain multiple quotes from contractors and ensure you understand local permitting fees.
5.2. Space and Aesthetics
Above-Ground: Require sufficient yard or side-lot space. Many homeowners screen these tanks with fencing or landscaping.
Underground: Preserve surface real estate for other uses (gardens, patios, driveways). However, you’ll need to ensure the area above the tank can handle the load of vehicles or other structures if you plan to build or park over it.
5.3. Climate and Temperature Considerations
Above-Ground: More prone to temperature swings; might need insulation in colder climates or shading in hot regions.
Underground: Ambient soil temperature often remains relatively stable year-round, which can help minimize algae growth and preserve water quality.
5.4. Maintenance and Longevity
Above-Ground: Easier to inspect and maintain. UV-resistant materials can last 15–25 years, depending on quality and climate.
Underground: Generally protected from environmental wear and tear, potentially offering longer lifespan, but repairs can be more complex and costly.
5.5. Water Quality and Treatment
Above-Ground: Requires protection from sunlight to deter algae growth; first-flush diverters and leaf screens are beneficial.
Underground: Less sunlight exposure and cooler water can reduce microbial growth, but you still need proper filtration for potable or semi-potable uses.
Note: For any indoor or potable application, consider adding filters (sediment, activated carbon) and disinfection (UV or chemical treatments) to meet health codes.
5.6. Regulations and Permitting
Regulations vary state by state and often county by county. Key points to consider:
Above-Ground: May face fewer restrictions, but some jurisdictions require permits if the capacity is above a certain threshold or if the tank is connected to household plumbing.
Underground: More likely to require engineering plans and permits due to excavation. Some areas have regulations on how far from structures and property lines the tank must be placed.
Example:
Texas actively promotes rainwater harvesting, often with rebates and relatively lenient permitting (Texas Water Development Board, 2005).
Colorado historically had more restrictive laws, though recent legislation allows limited home use of rain barrels (Colorado General Assembly, 2016).
Always consult local building codes and water authorities before purchasing a tank.
6. Which Tank Type Is Best for You?
Choosing between above-ground and underground tanks hinges on these critical considerations:
Budget: Above-ground tanks generally have lower upfront costs.
Lot Size and Layout: Underground tanks free up surface space but need suitable excavation conditions.
Local Climate: Underground tanks offer more stable water temperatures, beneficial in extreme climates.
Maintenance Preferences: Above-ground tanks are easier to visually inspect and repair; underground tanks are more hidden but potentially require specialized services for maintenance.
Aesthetic Goals: If you want to minimize visual impact, an underground system may be the better choice.
Pro Tip: Some homeowners use a hybrid approach—they install an underground tank for large-scale storage and then utilize a small above-ground barrel for quick, convenient access to water for gardening.
7. Case Studies and Practical Examples
Urban Residential Property in Austin, Texas:
Homeowners installed a 1,000-gallon above-ground plastic cistern, screened by lattice and climbing vines. Initial costs were kept low by avoiding excavation. They received a partial rebate from the City of Austin’s water conservation program.
Suburban Home in Seattle, Washington:
A homeowner buried a 2,500-gallon concrete cistern to maximize yard space for a garden. Seattle’s frequent rainfall keeps the cistern full year-round. Maintenance is more involved, but the aesthetic and yard usage benefits outweighed the higher cost.
Rural Retreat in Arizona:
Due to rocky ground conditions, the owners opted for multiple medium-sized above-ground metal tanks instead of a large underground system. This approach simplified installation but required additional shading to keep water temperatures down.
Each example illustrates how local climate, personal preferences, and budget constraints shape the decision between above-ground and underground storage solutions.
8. Conclusion
Rainwater harvesting is an effective strategy for enhancing water security, cutting costs, and promoting environmental responsibility. Whether you choose an above-ground or underground storage tank depends on factors like budget, property characteristics, local climate, and aesthetic preferences.
Above-Ground Tanks offer lower upfront costs, easier installation, and simpler maintenance.
Underground Tanks provide better temperature regulation, preservation of yard space, and aesthetic advantages but come with higher initial expenses and more complex maintenance.
By understanding these trade-offs, researching local regulations, and possibly consulting a qualified installer or engineer, you can select a system that effectively meets your household’s needs. With proper planning and consistent maintenance, either option can provide decades of reliable water storage—enabling you to conserve resources, lower utility bills, and safeguard against water shortages.
9. References
American Rainwater Catchment Systems Association (ARCSA). (n.d.). Rainwater Catchment. https://www.arcsa.org/
City of Austin. (n.d.). Water Conservation Rebates and Programs. https://www.austintexas.gov/department/water
Colorado General Assembly. (2016). Rain Barrel Legislation (HB16-1005). https://leg.colorado.gov/
King County. (n.d.). Rain Barrel and Cistern Programs. https://www.kingcounty.gov/
Texas Water Development Board. (2005). The Texas Manual on Rainwater Harvesting. https://www.twdb.texas.gov/
U.S. Environmental Protection Agency (EPA). (n.d.). Rainwater Harvesting Policies. https://www.epa.gov/
Disclaimer: This blog post is for informational purposes only and does not constitute legal, engineering, or professional advice. Always consult local building codes, water management authorities, and qualified professionals to ensure compliance and safety.