1. What is rainwater harvesting?
The practice of rainwater harvesting involves the collecting, storing, and often cleaning of rainwater to use it as an alternative water source as needed. Rainwater is commonly collected from roofs, stored in rain barrels or storage tanks, and can be used for any water-requiring activity as long as it has been treated properly for the application.
2. Why should I consider harvesting rainwater?
You should consider rainwater harvesting for the potential benefits the practice provides. Active rainwater harvesting promotes water sustainability, environmental management, and regional ecological balance of local water resources, reduces reliance on municipal water, lowers water bills, and provides a naturally soft, chemical-free water source that is beneficial to plants, landscaping, animals, and household chores.
3. How does a rainwater harvesting system work?
Rainwater harvesting systems typically work the same way but may differ in the exact setup and specific accessories being used. Rainwater falls and is collected from the roof, channeled through the conveyance system, filtered by accessories, and stored in a tank, or other reservoir, for use when needed.
4. What are the parts of a rainwater harvesting system?
A rainwater system often features a catchment area (usually a roof), a conveyance system (gutters, downspouts, pipes), accessories (leaf eaters, first flush diverter), a storage tank or tanks, and a distribution system (hoses, pipes, and/or water pumps).
5. Can rainwater harvesting be used for drinking?
Yes, harvested rainwater can be used for drinking but it should first be properly filtered and treated. Although rainwater itself is typically clean and safe to drink, the problem lies in microorganisms and other pollutants the rainwater can pick up as it flows over a roof and through gutters. Such contaminants can make you sick or present health concerns, particularly over time. If you plan to harvest rainwater for drinking or other potable uses, it is imperative to have an appropriate purification system in place.
6. Is rainwater harvesting expensive?
The cost of a rainwater harvesting system is entirely dependent on the complexity of the setup, the system size, and your intended water use. A rain barrel or IBC tote setup simply used to water a garden or landscaping will cost much less than a water pump pressurized rain harvest setup for an irrigation system or a full potable water system used to supply water to a home, business, or industry application. A simple rainwater harvesting setup can be very inexpensive, especially if a low cost rain barrel or IBC tote is used, and can cost less than $100 to $500.
7. What materials are rainwater tanks commonly made from?
Rainwater harvesting tanks are commonly made from either high density polyethylene (HDPE), fiberglass, galvanized steel, or stainless steel. Rain barrels are often made from HDPE, galvanized steel, or stainless steel metal. IBC totes are often made from HDPE. Bulk rainwater tanks are available made from each of the different materials. HDPE and fiberglass are synthetic materials that are lightweight, rust-proof, corrosion resistant, and often less expensive compared to metal rain tanks. Galvanized steel and stainless steel rainwater tanks also resist corrosion and are typically heavier and cost more compared to polyethylene or fiberglass tanks.
8. Which tank material type is best for rainwater harvesting?
The best rainwater tank material type will depend on your needs. For rainwater storage volume, galvanized steel water tanks and fiberglass tanks provide the largest capacity of available rain tank products with volumes up to 100,000 gallons or more. For a variety of different container types to choose from, less weight that is easier to move, and less cost, polyethylene rain tanks make the best choice. In terms of lifespan, all materials can provide many years of use if properly cared for and kept.
9. Which rainwater harvesting tank is best?
The best rainwater harvesting tank will depend on how much rain you want to collect, how much land space is available, and the constraints of your budget. The best rain tank for volume will be a galvanized steel or fiberglass tank. The best rain tank for land space will be an underground water tank or a doorway tank. The best rain tank for a budget will be a rain barrel, IBC tote, or small poly water tank.
10. How do I choose the right size for my rainwater tank?
To choose the right rainwater harvesting tank in size, know: your catchment area size, regional annual rainfall, and a good estimate of how much water you need or plan to use. There is little need to purchase a large tank that will never get full due to limited rainfall, a small catchment area, and regular use. Similarly, a tank that is too small for the rainfall and catchment area will result in overflow and the excess rainwater harvested unable to be used. Here, however, you could add an additional rain tank to collect any overflow.
11. What is the lifespan of a rainwater harvesting system?
The lifespan of a rainwater harvesting system will depend on the quality and care of its individual components. All of the materials used to make most modern rainwater harvesting equipment are long-lasting and durable. With quality products, well-maintained systems can last for several decades. Note, this is a general expectation and possibility of real results, but is not meant as a guarantee as actual lifespan can vary.
12. How do I maintain a rainwater harvesting system?
Regular rainwater harvesting maintenance can include cleaning gutters, the roof, accessories such as debris screens and first flush diverters, cleaning the container itself, inspecting tanks and connections for damage or leaks, and ensuring pumps and treatment systems are properly working. The amount and frequency of this maintenance will depend on the amount of rain, the amount of nearby vegetation, and how clean you need the setup and rainwater to be. Simple rainwater harvesting setups, such as a homeowner using a rain barrel to water a garden, may not have some of these parts and may not require much maintenance.
13. Can I use harvesting rainwater for my entire household?
Yes, harvested rainwater can be used to provide the water needed for an entire household. This includes drinking, cooking, bathing, laundry, flushing toilets, cleaning, and outdoor water uses such as gardening, landscaping, animals, and washing vehicles. To use rainwater as your home’s water supply (i.e., potable use) will require a complete rain harvesting system; i.e. debris screens, bulk volume water tank, water pump, plumbing and connections, cartridge filtration, and a treatment or purification method such as UV light treatment, chlorination, or reverse osmosis. Note, if you live in the United States, some states have restrictions on using rainwater for potable applications, so always verify it is legal in your state and understand any requirements before starting your project.
14. Is rainwater harvesting legal? Are there any legal restrictions on harvesting rainwater?
Laws and regulations vary by region and sometimes by city, this includes for rainwater harvesting. At the time of this writing, the States of Utah and Nevada have restrictions on how much rainwater can be collected, and the States of Illinois and Georgia (excluding Atlanta) restrict using rainwater for potable applications. Many other states do not have standards, codes, or guidelines on rainwater harvesting practices or for indoor uses.
15. Is rainwater harvesting encouraged? Are there any government-supported incentives?
Yes, and yes. Rainwater harvesting is encouraged, and several US states and cities currently have different incentives supporting the practice. Rainwater harvesting incentives are more frequently offered by individual cities, sometimes by counties or water companies. State-level support is often in the form of a tax rebate, credit, or fund, which is often dedicated to specific project types.
16. Can rainwater harvesting systems be used during all seasons?
Yes, rainwater harvesting can be done throughout the seasons but it will depend on local weather conditions such as rainfall and temperature. A rainwater system will have little use if there is no rain and the tank is dry. Also, during the winter season, freezing temperatures can prevent the collection of more water and its use. For more info on this, see How to Protect a Rainwater Tank from Freezing.
17. Can rainwater harvesting help during droughts?
Yes, rainwater harvesting can serve as an alternative water supply during periods of drought if rainwater is collected during the wet season and stored for use during the dry season. Depending on the volume of regular rainfall and size of the rain tank and catchment areas, this method could potentially supply tens of thousands of gallons of water during droughts. Some agriculture farms have used rainwater harvesting to collect and supply over 100,000 gallons of water for on-site use.
18. Can I install a rainwater harvesting system myself?
In most cases, yes, you can DIY and install your own rainwater harvesting equipment. Simple setups typically only involve placing the container, connecting a downspout, and perhaps installing a debris screen or first flush. Larger, more complex systems will require a thorough understanding as well as the capability to choose and set up a water pump (or pumps) as well as running and connecting plumbing. While this can be DIY, for indoor rainwater supply, there are often codes and guidelines that must be followed. Some states even require a licensed professional to perform this work.
19. What are the parts of a rainwater harvesting system?
Rainwater harvesting systems typically consist of four (4) main parts: the catchment area (e.g., roof), the conveyance system (e.g., gutters and downspouts), the collection container (e.g., barrel, IBC, tank), and a means to access and use the rainwater. Rainwater harvesting accessories (e.g., leaf eaters, tank screens, first flush diverter) are not a necessity but are generally recommended due to the benefits they provide. Water pumps and water treatment units (e.g., cartridge filters, UV lamps) are only necessary for rainwater applications that require them, such as when pressurized water for irrigation or potable grade water for consumption is needed.
20. You mention rainwater harvesting accessories, what are they and what do they do?
Rainwater harvesting accessories include debris screens, diverters, solar shields, flap valves, air gaps, overflow kits, tank gauges, water pumps, and water treatment systems. To learn more about these accessories, what they do, and details on installation, see our Rainwater Harvesting Accessory Guide.
21. How does a first flush diverter work?
A first flush diverter is a rainwater add-on accessory designed to divert the initial runoff of a rainfall event away from the storage container. This initial runoff often contains higher levels of dust, airborne particulates, bird droppings, leaves, and other debris compared to rainwater runoff later in the rain event. So, a first flush captures the dirtier, initial rainwater until the diverter is full so cleaner rainwater reaches the rain tank.
22. What is the role of a water pump in a rainwater harvesting system?
A water pump is used to distribute rainwater from the container so the water can be used where and how it is needed. A water pump is used to increase water pressure and water flow rates and is often included in setups with long hoses, spray nozzles, irrigation systems, sprinklers, or indoor applications. When gravity-provided water pressure (which is fairly small) is not enough for rainwater use, a water pump will be necessary.
23. What is rainwater harvesting’s impact on the environment?
Rainwater harvesting has a positive environmental impact by reducing the use of municipal water supplies sourced from regional water, which also reduces the energy used to treat and distribute this water, reduces groundwater use, and lessens stormwater runoff to reduce erosion, flooding, and non-point source pollution. Overall, rainwater harvesting is a positive contribution to water conservation efforts and efforts to reduce our carbon footprint.
24. What types of roofs are best for rainwater harvesting?
The best roofs to harvest rainwater from include seam metal roofing made from finished steel, slate tile roofs, composite shingle roofs, FDA-approved EPDM roofs, and lastly asphalt shingle roofs.
25. Does the quality of rainwater vary?
Yes, rainwater quality can depend on environmental factors such as local air quality and vegetation. Rainwater harvested in urban and industrial areas or near large-scale agriculture operations may contain more pollutants than rainwater collected in rural areas. The amount of nearby vegetation can affect rainwater quality in terms of debris and pollen.
26. Is rainwater harvesting practical in urban areas?
Yes, rainwater harvesting is actively practiced in many urban areas by the residents there. The scale, however, may be smaller due to space constraints and the water quality may be impacted by increased air pollutants, yet the practice is still a viable and effective water conservation method. A first flush diverter could help improve water quality. To learn more about a rain diverter and how it could help harvest rainwater in an urban area, see our First Flush Diverter Explained.
27. Can a rainwater harvesting system be installed in an existing building?
Yes, a rainwater harvesting system can be retrofitted into an existing building. The cost and ease of the installation process will depend on the building (often related to its age) and its plumbing system. Many times, this involves connecting the rainwater system to the building’s main incoming water supply line while including safeguards to prevent backflow such as a reduced pressure zone (RPZ) backflow assembly. Always check and follow any state-mandated requirements.
28. Can rainwater harvesting systems be used in multi-story buildings?
This generally applies to large-scale rainwater harvesting and indoor supply scenarios. In such cases, yes, rainwater harvesting can be used in multi-story buildings when professional planning is performed to ensure the safe and efficient collection, storage, and distribution of the harvesting rainwater. The increased size of many multi-story buildings, such as multi-family residences, makes rainwater harvesting an excellent option due to the large water volumes that can potentially be collected.
29. Does the color of the storage tank affect the quality of the stored water?
The color of a rainwater storage tank can affect the stored water quality in terms of the amount of light the tank allows through and the growth of algae. Lighter colored tanks generally allow more sunlight in compared to darker colored tanks, making dark-colored tanks preferred for rainwater harvesting as less light penetration means less algal growth.
30. What points are important when choosing a location for a rainwater tank?
Important points in choosing a rainwater tank location include proximity to the catchment area and point(s) of use, ground stability, accessibility for maintenance, amount of sunlight exposure, and lastly, personal aesthetic preference.
31. What are the benefits of underground rainwater storage tanks?
The benefits of an underground rainwater storage tank are several. An underground tank saves space, maintains water temperature, maintains cooler temperatures, slows bacterial growth, prevents algae growth, and is less susceptible to damage. On the other hand, underground water tanks require more installation effort and associated costs. For more on this, see How to Install an Underground Water Tank.
32. What happens when the rainwater storage tank is full?
When the rainwater tank becomes full, any extra incoming rainfall will be diverted to the container’s overflow port if one is present. Most dedicated rainwater tank products include a pre-installed overflow port. If an overflow is not present, a kit can be purchased and installed, otherwise, excess rainwater will flow out from the container in whatever way possible.
33. What is the best way to manage rainwater tank overflow?
The best way to manage overflow from a rainwater tank is to discard the water away from the base of the tank and still put the water to good use if possible. This can include connecting another tank to harvest the water or setting up a hose or piping to direct the water to a nearby garden, landscape, water feature, drainage field, or water body.
34. Can I use rainwater in my washing machine?
Yes, using harvested rainwater for a washing machine is a recommended use and is beneficial because rainwater is naturally soft (low in minerals) compared to typical municipal or groundwater supplies. This quality makes rainwater a better choice for washing and maintaining your clothes and can reduce the amount of detergent that is needed.
35. Can I use rainwater in my dishwasher?
Yes, harvested rainwater can be used in a dishwasher as long as debris and particles are removed that could clog and/or damage the dishwasher system.
36. Can harvested rainwater be used for cooling systems?
Yes, using rainwater harvesting to supply water for commercial cooling systems is a primary, recommended use of large-scale rainwater harvesting practice. Several organizations, institutions, and universities have either experimented (for research) or currently use harvested rainwater for their onsite cooling systems. Due to being naturally soft, rainwater makes a better choice for cooling equipment while also being cost-effective and environmentally friendly.
37. Can I use harvested rainwater in my swimming pool?
Yes, using rainwater harvesting to supply water for your swimming pool is an excellent way to conserve water. However, it is important to remember that rainwater must be properly treated to keep the pool a safe and clean swimming environment. This may be as simple as adding pool treatment chemicals as you would normally do, especially if your rain system is already set up to remove debris.
38. What causes bad odors in my rainwater tank, and how can I prevent them?
Bad odors in your rainwater tank are most often caused by organic matter that has reached your container and is decomposing. Common organic matter includes leaves, needles, sticks, seeds, petals, pollen, animal droppings, small animals, insects, fur, and feathers. A leaf eater and tank screen accessory are highly effective in removing larger debris, while a first flush diverter can be used to remove some smaller contaminants, therefore keeping them out of the tank and preventing bad odors.
39. How does a rainwater harvesting system affect my home insurance?
In most cases, installing a rainwater harvesting system should not negatively affect your home insurance policy. However, due to varying differences across policies, it is always a good idea to check with your insurance provider, particularly if you plan to install a large volume rain tank. If you plan to install a rain system to provide indoor water, check with your provider.
40. What is the impact of rainwater harvesting on my property value?
Installing a rainwater harvesting setup can potentially cause an increase in your property value. A system and the practice are seen as environmentally friendly and as a feature that can lower water bills, which can make the property more attractive to potential buyers.
41. Can I drink rainwater directly from my roof?
Drinking rainwater directly from a roof is not recommended without first treating and/or filtering the water before consumption. This is due to potential pollutants the rain can pick up as it falls through the atmosphere (airborne gases) and flows over the roof (animal droppings, remains, decomposing vegetation). Rainwater is typically much cleaner after the first five minutes of active rainfall. This is due to a scrubbing effect that happens as rain washes the pollutants away.
42. Does the pH of rainwater affect its use?
Rainwater is naturally slightly acidic due to its purity, effectiveness as a solvent, and carbon dioxide it picks up from the atmosphere. The pH of rainwater does not typically affect what it can be used for. However, it is the primary reason why copper pipes are not recommended for handling rainwater. The slightly lower pH of rainwater can cause damage to copper pipes over time and lead to pinhole leaks.
43. How does a slow sand filter work in a rainwater harvesting system?
A slow sand filter works similarly to home water filtration products. The filter uses a bed of sand that allows rainwater to pass through but filters out particles and microorganisms that may be in the water. As rainwater passes through the sand bed, bacteria may form a layer on top, which further aids in the purification process.
44. Can rainwater harvesting systems be integrated with smart home technology?
In many cases, a rainwater harvesting system can be integrated with smart home technology to allow remote control and monitoring of the system, and even work together with weather forecasting to maximize the system’s efficiency. Note that this will require purchasing the proper products and having the technical know-how to set this up.
45. How does rainwater harvesting help in reducing the energy footprint?
By reducing the amount of municipal water supply being used by a home or business, the amount of electrical energy necessary to collect, treat, and distribute the municipal water from the source to the point of use will also be reduced. Therefore, the less water you use that comes from somewhere else, the less electricity overall being used. This connection between water and electricity is known as the water-energy nexus. See our post for more on the water-energy nexus and how rainwater harvesting can play a role in current world problems.
46. Can rainwater harvesting systems cause mosquito infestations?
Yes, an improperly designed and poorly-cared for rainwater harvesting setup can cause a mosquito infestation. On the other hand, a properly designed and cared-for setup should not cause a concern with mosquitoes. To keep mosquitoes out, a proper rainwater setup may include a tank screen, tight-fitting lid, or manway cover, an inlet pipe screen (flap valve), and an overflow pipe screen (air gap or flap valve). You simply need to keep mosquitoes from being able to reach the water inside your rain container, and the accessories mentioned can be used to do this.
47. What precautions should be taken when using harvested rainwater for edible plants?
If the rainwater is not treated, choose to apply the water directly to the soil rather than on the plant itself to minimize any potential risk. Using debris screens and a first flush diverter can improve water quality. Harvested rainwater is generally not recommended to wash or rinse edible plants before consumption. Rinsing food crops should be done with municipal water or properly treated rainwater.
48. Does rainwater need to be treated when used for non-potable purposes?
Treating rainwater is not typically required for non-potable uses such as irrigation or watering a garden and landscape. For indoor non-potable uses, such as flushing toilets or washing clothes, some level of treatment is recommended and may even be required by local legal codes and standards. Generally, if a water pump will be used and/or equipment with potentially small openings (e.g., sprinklers), then some treatment or filtration should be done to prevent small debris or sediment from causing clogs.
49. How can I ensure the harvested rainwater is safe for drinking?
To ensure harvested rainwater is safe for drinking, you must use appropriate filtration and purification methods to remove particulates, chemicals, microorganisms, and any potential pathogens. Multistage cartridge filtration down to 4 or 5 microns in size is a common option for filtration. UV sterilization, reverse osmosis, and chlorination are common options for purification. Regular maintenance and replacement of working parts, such as filters and lamps, is also required. Water quality tests are recommended to ensure the rainwater is drinking water safe.
50. How does the quality of harvested rainwater compare to well water or municipal water?
The quality of rainwater can be excellent and is often considered superior to well water or municipal water. Compared to well water, rainwater doesn’t have the minerals that cause hardness, sulfides that cause rotten egg smell, and concerns with contaminated groundwater. Compared to municipal water, rainwater doesn’t have hard minerals, potential residual chemicals from treatment, and concerns with forever chemicals or other contaminants. However, unlike municipal and well water supplies microorganisms may be present and appropriate treatment will be necessary for potable-grade rainwater.
51. What happens to the rainwater harvesting system during heavy rainfall?
During heavy rainfall events, the storage container can fill up rather quickly. Once full, any excess water will overflow from the container, which is best if controlled in some manner, such as with a pipe or hose, to direct the water away from the container and any nearby building or foundation. The volume of water during heavy rainfall can be hundreds of gallons, which if unmanaged, can cause damage to soil or foundations, especially over time.
52. Does rainwater harvesting efficiency depend on the local climate?
Yes, rainwater harvesting, being entirely dependent on precipitation, is directly affected by the local climate and annual, average rainfall. Regions with high yearly rainfall can realize a greater rainwater harvest compared to more arid regions. In all cases, however, a larger catchment area will harvest more rainwater and could potentially be used to compensate for less rainfall in drier regions.
53. How long can I store the harvested rainwater?
The storage life of harvested rainwater will depend on different factors such as the cleanliness of the roof, gutters, and storage tank, whether debris screens and a first flush are being used, and whether you treat the water. If rainwater is harvested, treated, and stored correctly, it can potentially last for several months.
54. Can I use drip irrigation or soaker hoses with my harvested rainwater?
Yes, a rainwater harvesting setup can be connected to a drip irrigation or soaker hose to distribute the water from the rain container to your plants. Vertical height and gravity pressure will be a key point in these uses. Consider slightly elevating the rain container by placing it on a pedestal or other platform.
55. What are the potential downsides of rainwater harvesting?
While rainwater harvesting has many benefits, some potential downsides may include the initial setup cost, ongoing maintenance, and rainfall variability that can cause inconsistent water supply.
56. Can businesses benefit from rainwater harvesting systems?
Yes, businesses can significantly benefit from rainwater harvesting. Due to large building sizes common to businesses, large volumes of rainwater can potentially be collected that could be used for operations such as landscaping, flushing toilets, industrial processes, watering livestock, cooling equipment, or cleaning vehicles. For a business to employ rainwater harvesting also demonstrates a commitment to environmental sustainability, which can increase the company’s public reputation. For more on this, see our post Rainwater Harvesting for Commercial Businesses and Beyond: A Green Initiative for A Sustainable Future.