Water is one of our most precious natural resources. With climate change and growing populations putting pressure on freshwater supplies around the world, more and more homeowners are looking to harvest rainwater to help meet their water needs. Implementing a residential rainwater collection system can provide a sustainable source of soft, pH neutral water for irrigation, washing, and other non-potable uses.
Overview of Rainwater Collection Systems
Rainwater harvesting refers to the capture, diversion and storage of rain that falls on a roof or other catchment area. The water is most often collected in tanks or cisterns rather than allowed to run off. This stored water can then be used for a variety of purposes around the home and garden.
There are two main types of residential rainwater collection systems:
Passive Systems
Passive systems collect rainwater that falls on the roof and divert it directly via gravity to wherever it will be stored and used. Gutters, downspouts, and piping deliver the water to the storage tank or cistern. Passive systems require no energy input and are generally the most affordable option.
Active Systems
Active rainwater collection systems utilize pumps to move water uphill from the collection point to the storage tank. These systems allow more flexibility in storage tank placement. They do require some energy input to run the pump.
Hybrid Systems
Some homeowners opt for a hybrid system that incorporates both passive and active elements. This allows gravity feed capture but also offers the ability to pump water to additional storage tanks at a higher elevation if desired.
Components of a Rainwater Harvesting System
While systems can vary, most residential rainwater collection setups contain the same core components:
Catchment Area
The catchment area is the surface upon which the rain falls and is collected. In most home systems, this is the roof. The material, style and size of the roof influence how much water can be captured. Metal and tile roofs are ideal, while composite shingles are less so. Larger collection areas equal more potential water.
Gutters and Downspouts
Gutters and downspouts capture the rainwater from the roof surface and transport it via gravity to the storage tanks or cisterns. Materials like metal, vinyl and plastic all work well. Ensuring gutters are clear of debris is key to optimal water flow.
Leaf Screens and First Flush Diverters
Leaf screens fit over downspouts and filter out leaves, seeds and other debris that can clog the system. First flush diverters route the first 10-15 gallons of water collected during each rain event away from the tank. This first flush washes away bird droppings, dust and other contaminants from the catchment area.
Storage Tanks/Cisterns
Storage tanks, often called cisterns, hold the harvested rainwater for future use. A variety of tank materials, shapes and sizes are available, from large-scale polyethylene to slim space-saving tanks. Location, intended use and local regulations impact tank selection.
Conveyance Systems
Pumps, pipes, tubing and valves make up the conveyance system that delivers collected rainwater from the catchment to the storage tank and then to points of use around the property.
Water Treatment System
For some uses, additional water filtration and purification may be desired. Options like slow sand filtration, UV light, and chlorination can help improve water quality.
Overflow Piping
Once storage tanks fill up, overflow pipes direct excess rainwater into landscaping, French drains or storm sewers so it doesn’t flood the foundation.
Benefits of Installing a Rainwater Collection System
Harvesting rainwater for residential use offers a number of benefits:
Cost Savings
Up to 50% reductions in household water bills are possible when utilizing stored rainwater for irrigation, laundry, toilets and other non-potable uses. This also reduces pressure on municipal water supplies.
Stormwater Reduction
Capturing rainwater at its source lowers the amount of stormwater runoff that can cause erosion and flooding risks. This also decreases contamination of local water bodies.
Supply Reliability
Accessing rainwater provides a water source not dependent on typical infrastructure. This improves self-reliance during power outages or water use restrictions.
Healthier Plants
The pH neutral water tends to grow stronger plants and vegetation compared to treated tap water high in salts, chlorine and fluoride.
Soft Water
Rainwater lacks the hardness minerals found in ground and surface water sources, so it gently cleans without deposits or residues.
Environmental Sustainability
Using locally sourced rainwater reduces energy consumption associated with pumping and treating centralized water. This supports green building practices.
Potential Drawbacks to Consider
While beneficial overall, rainwater harvesting systems also come with some potential drawbacks to note:
- Upfront costs can be high, from $3,000 to over $10,000 depending on system scale. However, long term savings often offset this expense.
- Careful maintenance is required, including checking gutters, testing water quality, inspecting the tank, and tuning up the system regularly.
- Backup water sources may be needed in times of drought when rainfall is scarce.
- Hard water buildup in drains and fixtures may occur over time if the soft rainwater makes up a significant portion of total use.
- Local permits and regulations apply. Water rights and usage laws vary.
- Roofwashers and disinfection methods are needed if using rainwater for drinking.
With forethought given to system design and proper maintenance, residential rainwater harvesting provides eco-friendly benefits for many homeowners seeking to decrease their environmental footprint and water bills.
How Much Water Can You Collect?
The amount of rainwater that can be captured and stored depends on several factors:
Roof Size
The larger the catchment area, the higher the rainwater yield. Typical roofs can generate anywhere from 600 to over 2500 gallons per inch of rain that falls.
Rainfall Volume
Geographic location and climate plays a major role. Arid regions with limited annual rainfall will collect substantially less than tropical or temperate regions with steady precipitation.
Storage Capacity
How much water can be captured and held for use depends on the storage volume of the rainwater tanks or cisterns. Larger storage capacity equals more rainwater available for use between rain events.
Usage Rate
The volume needed to meet the household’s intended water usage impacts how much should be stored. Prioritizing rainwater for high-demand uses like irrigation allows for greater capture and savings.
A general estimate is 600 to 1500 gallons of water can be collected per inch of rain from a typical residential roof. With careful monitoring of rainfall amounts, tank levels, and household uses, optimal system performance can be achieved.
Rainwater Collection System Sizing
Properly sizing your residential rainwater harvesting system is crucial to maximizing water savings while avoiding wasted investment in overcapacity. Follow this process to right-size your system:
Calculate Catchment Area
Measure roof dimensions to determine surface area in square feet. Account for all connected areas that direct rainwater to your catchment.
Estimate Annual Rainfall
Review rain gauge data to determine average annual inches of precipitation for your location that you can collect from.
Define Intended Uses
Detail which applications you want to direct harvested rainwater towards, like outdoor irrigation, toilet flushing, laundry, etc.
Estimate Usage
Calculate approximately how much rainwater you’ll need for defined uses based on household occupancy and behaviors.
Storage Capacity
With catchment area and rainfall data, map out required storage in gallons to meet your intended usage. Allow for some reserve capacity.
System Design
Using your storage needs and site layout, design optimal system components like tank size and numbers, conveyance methods, water treatment needs and more.
Sizing rainwater harvesting systems for your specific conditions maximizes their performance and return on investment. Consider enlisting professional assistance from experienced rainwater installers if desired.
Choosing Where to Locate the Rainwater Storage Tank
Determining where to locate the rainwater storage tank requires careful consideration of several factors:
Convenience
The tank should be sited close to points of use for efficient distribution to irrigation systems, hose bibs or other applications. This also keeps conveyance costs down.
Elevation
Gravity feed tanks work best slightly uphilled from end uses. If sited lower, a pump system will be required to convey water. Consider site contours.
Accessibility
The storage tank must be accessible for regular inspections, maintenance, cleaning and supplementation from other sources like municipal water if needed.
Soil Conditions
Tanks require a stable, compacted base. The weight of full tanks can exceed 6,000 pounds, so soft soils or slopes may dictate relocation or foundation improvements.
Aesthetics
Some homeowners prefer to visually conceal large storage tanks behind fences, vegetation or within accessory structures. This should not limit access though.
Lot Space
Available room on the property often dictates placement. Side and rear lot spaces are typical locations to provide usable area above ground tanks.
Local Codes
Zoning, permits, setbacks from property lines or buildings and other codes may apply. Research requirements for your area.
With an understanding of your intended uses, site logistics and regulatory environment, an ideal rainwater tank location can be selected.
What Types of Tanks Can You Use?
There are several common options when selecting a rainwater storage tank or cistern for residential use:
Above Ground Tanks
The most economical and common choice is above ground tanks made from plastic, concrete, metal, fiberglass or wood. These are best suited for outdoor installation and range from 100 to over 10,000 gallons.
Below Ground Tanks
Also called cisterns, these tanks are buried, often under driveways, patios or other hardscapes. They hold large volumes but do require excavation. Underground concrete cisterns are common.
Bladder Tanks
Flexible bladder tanks can conform to available spaces and hold 500 to 1,000 gallons. Often used for basement installations, they are pricier but very space efficient.
Rain Barrels
Basic and inexpensive, these small (50-80 gallon) plastic barrels simply capture rooftop runoff. They are good for small applications like water gardens. Connecting several together provides more storage.
Repurposed Tanks
Some turn salvaged bulk tanks, food vessels, silos and other containers into budget rainwater tanks. Proper cleaning and sealing is essential for drinking water applications.
The optimal tank type, size, height, and number depend on your budget, space, and intended water uses. Consult with qualified rainwater harvesting professionals for the best storage setup for your residential site.
Water Treatment Options for Harvested Rainwater
While relatively clean, untreated rainwater isn’t recommended for direct potable use. Here are some treatment options for improving quality:
Filtration
Slow sand filtration, membrane filters and sediment traps all remove particulates for basic cleaning. This works well for irrigation uses.
First Flush Diverters
The first 10-15 gallons of rainwater washes contaminants from the catchment area away from storage tanks to improve quality.
UV Disinfection
Ultraviolet systems inactivate microorganisms without chemicals, though particles can limit effectiveness. Good supplemental treatment.
Chlorination
Approved chlorine dosing can disinfect rainwater of bacteria and pathogens for washing or drinking purposes when tested properly.
Boiling
Vigorous boiling of harvested rainwater will kill microbes, though it does not remove minerals or other particles from the water.
Ozonation
Ozone gas injections can disinfect and deodorize rainwater via oxidation. Requires proper on-site generation equipment.
For potable usage, often a combination of filtration, additives like chlorine, and testing is used to ensure the water is safe and pathogen-free after treatment. Consulting qualified water quality professionals is recommended.
Typical Costs Associated with Rainwater Collection Systems
Typical costs for a complete residential rainwater harvesting system:
- Gutters/Downspouts: $3-$7 per linear foot
- Leaf Screens/Roof Washers: $50-$200 each
- Standard Storage Tanks: $1-$2 per gallon
- Tank Foundations/Pads: $500-$1000
- Pumps: $250-$1000
- Pipes/Valves/Fittings: $5-$20 each
- Slow Sand Filtration: $1000-$3000
- General Labor: $50-$100 per hour
Other potential costs:
- System Design Fees: $500-$1500
- Excavation for Buried Tanks: $2000-$5000
- Cistern Delivery/Installation: $1000-$5000
- County Permits: $50-$500
- Electrician for Pump Install: $50-$100 per hour
Total System Cost: $3000-$12,000 on average based on size, components, complexity and labor. DIY systems with used components can reduce costs substantially.
Ongoing annual maintenance costs average $100-$300. While not inexpensive, rainwater systems yield substantial water savings and environmental benefits for years to come.
Typical Maintenance Requirements
To keep your residential rainwater harvesting system performing optimally, follow these maintenance practices:
- Inspect and clear gutters seasonally or after heavy leaf falls
- Check screens/filters for debris and replace as needed
- Inspect tanks for leaks, cracks or deterioration annually
- Verify water quality with yearly tests for bacteria
- Have a professional tank cleaning every 3-5 years
- Repair any damaged parts like seals, pipes, or pumps immediately
- Follow all maintenance directions for pumps, valves and other system components
- Watch for leaks, unusual noises, pooling water or other issues indicating problems
- Keep accurate records of all maintenance and repairs performed
Well maintained systems can function effectively for 20+ years. Neglected maintenance can lead to poor water quality, leaks, and system failures. Consider a service contract with qualified installers for periodic upkeep.
Signs It’s Time to Upgrade or Replace Your Existing Rainwater Harvest System
Indications your residential rainwater harvesting system may need an upgrade or replacement:
- Leaking tanks or pipes, or visible corrosion and rot on components
- Gutters frequently overflowing during rains
- Pumps requiring frequent repairs and replacements
- Sediment buildup in tanks requiring very frequent cleanouts
- Water tests indicating bacteria levels are no longer safe
- Visible cracks, dents or patches in storage tanks
- Difficulty keeping up with household water demands
- Parts and components no longer available or supported
- Technology advances making upgrades worthwhile
Depending on the scale of needed repairs, it may become more cost and time effective to do a full system replacement rather than ongoing repairs. New systems can take advantage of improved tank materials, higher capacity pumps, and smarter controls.
If system expansions like adding additional catchment area, storage capacity or new distribution lines are desired, this indicates a major upgrade is beneficial rather than just replacements.
Carefully evaluate the costs, benefits and value proposition when determining if maintaining and repairing your existing residential rainwater harvesting system still makes sense, or if replacement provides better long term performance.
Homeowner Association Rules About Rainwater Collection Systems
Homeowners’ associations (HOAs) and community rules can impact your ability to install a rainwater harvesting system. Here are some best practices:
- Review all HOA covenants, conditions and restrictions for language pertaining to architectural guidelines, hardscape and landscaping modifications, and water usage restrictions.
- Clearly understand design guidelines for visible components like above ground tanks, their sizing/locations, and screening methods like fencing.
- If required, complete the application process for architectural review board (ARB) approval as early as possible, providing all requested plans and specifications.
- Emphasize sustainability benefits and that carefully planned rainwater capture improves aesthetics by facilitating a thriving landscape.
- Offer to give community presentations about the benefits of residential rainwater harvesting to build support.
- Start with smaller tank sizes and less complicated system components and communicate future expansion plans if desired.
- Ensure compliance with all local building codes and permits to avoid issues.
- If objections arise, request hearings with the HOA board to make your case or explore alternatives like smaller tanks or relocated siting.
With education and smart planning, residential rainwater collection systems can usually comply with HOA requirements through open communication, savvy design adaptations and accentuating the positives for the whole community.
Getting Permits and Complying with Codes for Your Rainwater System
Local codes and permitting requirements govern installation of residential rainwater harvesting systems. Here are key steps for smooth compliance:
- Research local plumbing, electrical, construction, zoning and water regulations that apply to components like outdoor storage tanks, buried cisterns, pumps, and drainage.
- Submit required applications and documents like system schematics for permits from agencies like municipal planning, building and health departments.
- Inspection of foundation pads, footings, underground electrical lines, and drainage may be required at set construction stages.
- Storage tanks usually must maintain setback minimums from property lines, buildings and septic systems.
- Backflow preventers, valves, and air gaps may be mandatory where potable and rainwater systems interconnect.
- Water quality testing and reporting is required for indoor potable use in some jurisdictions.
- Licensing, bonding and inspections of hired contractors may be needed.
- Any homeowners’ association requirements must also be incorporated.
Coordinating early with inspectors ensures your rainwater collection system will meet all applicable building codes and standards. Avoid headaches by checking requirements before installation. Consider consulting services to facilitate smooth permitting.
Hiring Professional Installers vs DIY Rainwater Collection Systems
Choosing between hiring professionals versus DIY installation comes down to:
Hiring Pros
- Ensures proper design, sizing and material selection for performance and durability
- Permits and inspections are facilitated by experienced contractors
- Licensed tradespeople have expertise for safe electrical, plumbing and excavation work
- Tanks and components are properly leveled, secured, connected and tested
- Responsibility for repairs/damages lies with the company
- Provides guidance on maintenance and future upgrades
DIY Install
- Minimizes upfront installation costs for budget-conscious homeowners