Rainwater harvesting is a technology that involves collecting rainfall in a reservoir or cistern. Although this water may be used as drinking water in some cases, water from a rain barrel or rainwater harvesting system is used for landscape irrigation or other non-potable uses. Rainwater collection can be particularly useful to home gardeners because it is better to water your plants with rainwater than tap water.
Rainwater is better for your plants than tap water because it does not contain the chlorine and other chemicals that are typically in municipal water. In addition, rainwater tends to be more acidic than tap water. This is important because water with a pH that is too high can raise the soil pH and make certain nutrients unavailable to the plant.
I am particularly interested in rainwater harvesting because it combines two of my favorite subjects – stormwater and gardening. As a stormwater engineer with a strong background in soil/plant science, I believe that most home gardeners could benefit from a rainwater harvesting system. Although the larger commercial systems can look intimidating, rain barrels are easy to install and use. The rest of this article will provide some background on rainwater harvesting and how to select the right system for you.
What is Rainwater Harvesting?
As previously discussed, rainwater harvesting, which is also called rainwater collection, describes a system that captures and collects rainfall. Water is collected from an impervious surface such as a rooftop or driveway and diverted to a cistern or reservoir. This water can be used for a variety of non-potable uses including landscape irrigation, toilet flushing, or car washing. The term rainwater harvesting is general and refers to systems of many sizes.
The term rain barrel refers to a small rainwater harvesting system that consists of a container that is at most 55 gallons. These types of systems work well for most home gardeners.
Rain barrels are a budget-friendly alternative to larger rainwater harvesting systems. They can be used to meet smaller water demands like watering home gardens or houseplants. Rain barrels are usually constructed from a 55-gallon container which are used to store a variety of materials. If you make your own rain barrel, it is important to clean the barrel to avoid putting any harmful chemicals on your plants.
Is Rainwater Harvesting Legal in the United States?
In the United States, there are no Federal regulations that restrict the use of rainwater harvesting. However, there are some states that have restricted rainwater collection in the past – specifically Western States. This is because these states’ water laws operate under a legal doctrine called Prior Appropriation. Prior Appropriation states that the first person to use water for a beneficial use such as agriculture has the right to continue to use that water for that purpose. This means the water falling from the sky has already been “assigned” to someone. Thus, by collecting rainwater, you are stealing the water from someone else.
Each drop of rain falling through the sky has already been allocated to a user. Leave the hose running between rinses while you wash your car and you won’t run afoul of the law; but if you gather a pailful of rainwater and pour on your tomato plant, look over your shoulder for a water cop. You will be preventing those raindrops from entering the watershed, depriving people downstream from the surrounding creeks and rivers of their rights to use their apportioned amounts of streamflow. The doctrine of prior appropriation comes crashing up against the imperative to conserve scarce water. Colorado made it legal for some homeowners to harvest rain and snow from their roofs. Tucson is encouraging its citizens to gather rainwater. Santa Fe made catchment devices mandatory for new dwellings. But, in Utah and Washington (with the exception of Seattle), harvesting raindrops is still a crime.
Stephen Grace, Dam Nation Documentary (2012)
Fortunately, many of these Western States have started relaxing some of their restrictions on rainwater harvesting. For example, the State of California passed Assembly Bill 1750 in 2012 which made it legal for residential and commercial landowners to collect rainwater. In addition, Colorado passed a law in 2016 that allowed residential landowners to install rainwater harvesting systems with a maximum capacity of 110 gallons. The collected rainwater can only be used for lawn and garden irrigation.
The table below summarizes the rainwater harvesting laws in each state. It is still a good idea to check your local laws before installing a rainwater capture system as some municipalities or homeowners associations may have certain restrictions or require permits.
| State | Rainwater Harvesting Legal? | Notes |
|---|---|---|
| Alabama | Yes | There are currently no regulations restricting rainwater collection |
| Alaska | Yes | Groundwater harvesting is restricted |
| Arizona | Yes | House Bills 2363 and 2830 made rainwater harvesting legal in Arizona |
| Arkansas | Yes | Rainwater harvesting systems must be used for non-potable purposes, designed by a professional engineer licensed in Arkansas, designed with appropriate cross-connection safeguards, and comply with the Plumbing Code |
| California | Yes | |
| Colorado | Yes | Rainwater harvesting systems can have a maximum capacity of 110 gallons and must be used on the property where it is collected for lawn/garden irrigation. |
| Connecticut | Yes | There are currently no regulations restricting rainwater collection |
| Delaware | Yes | There are some incentive programs for rainwater harvesting. |
| Florida | Yes | Some counties have tax incentive or rebate programs. |
| Georgia | Yes | Collected rainwater can only be used outdoors. |
| Hawaii | Yes | There are currently no regulations restricting rainwater collection. |
| Idaho | Yes | There are restrictions on rainwater that has entered natural waterways. |
| Illinois | Yes | Within 120 days after a homeowners’ association is formed, the association shall adopt an energy policy statement that indicates whether rainwater harvesting is allowed. |
| Indiana | Yes | There are currently no regulations restricting rainwater collection. |
| Iowa | Yes | There are currently no regulations restricting rainwater collection. |
| Kansas | Yes | A permit may be required from the Department of Agriculture. |
| Kentucky | Yes | There are currently no regulations restricting rainwater collection. |
| Louisiana | Yes | There are restrictions on large cisterns. |
| Maine | Yes | There are currently no regulations restricting rainwater collection. |
| Maryland | Yes | Some counties offer incentives. |
| Massachusetts | Yes | There are currently no regulations restricting rainwater collection. |
| Michigan | Yes | There are currently no regulations restricting rainwater collection. |
| Minnesota | Yes | There are currently no regulations restricting rainwater collection. |
| Mississippi | Yes | There are currently no regulations restricting rainwater collection. |
| Missouri | Yes | There are currently no regulations restricting rainwater collection. |
| Montana | Yes | There are currently no regulations restricting rainwater collection. |
| Nebraska | Yes | There are currently no regulations restricting rainwater collection. |
| Nevada | Yes | Under NB74, which was passed in 2017, you must be granted a water right to collect rainwater. |
| New Hampshire | Yes | There are currently no regulations restricting rainwater collection. |
| New Jersey | Yes | Some property owners may be eligible for a rebate for their rainwater collection system. |
| New Mexico | Yes | There are currently no regulations restricting rainwater collection. |
| New York | Yes | There are currently no regulations restricting rainwater collection. |
| North Carolina | Yes | North Carolina State University’s Biological and Agricultural Engineering Department has published several great resources for rainwater harvesting. |
| North Dakota | Yes | There are currently no regulations restricting rainwater collection. |
| Ohio | Yes | There are currently no regulations restricting rainwater collection. |
| Oklahoma | Yes | There are currently no regulations restricting rainwater collection. |
| Oregon | Yes | Rainwater harvesting systems can only collect water from rooftops. |
| Pennsylvania | Yes | There are currently no regulations restricting rainwater collection. |
| Rhode Island | Yes | There are tax incentives for systems with a capacity of at least 50 gallons. |
| South Carolina | Yes | There are currently no regulations restricting rainwater collection. |
| South Dakota | Yes | There are currently no regulations restricting rainwater collection. |
| Tennessee | Yes | There are currently no regulations restricting rainwater collection. |
| Texas | Yes | The catchment system must be incorporated into the building design, and a permit is required. |
| Utah | Yes | The direct collection of rainwater on land owned or leased by the person responsible for the collection. You cannot store more than 2,500 gallons, and each container cannot have a capacity greater than 100 gallons. |
| Vermont | Yes | There are currently no regulations restricting rainwater collection. |
| Virginia | Yes | There is an income tax credit available to those who install rainwater harvesting systems. |
| Washington | Yes | There are currently no regulations restricting rainwater collection. The City of Seattle strongly encourages rainwater harvesting. |
| West Virginia | Yes | There are currently no regulations restricting rainwater collection. |
| Wisconsin | Yes | There are currently no regulations restricting rainwater collection. |
| Wyoming | Yes | There are currently no regulations restricting rainwater collection. |
Selecting The Right System For You
Before purchasing your own rain barrel, there are some things to consider to make sure you are purchasing a system that will fit your needs. This section will help you pick the right rain barrel for your garden.
Sizing The Rain Barrel
The size of your rain barrel depends on a few factors including the catchment area, the amount of water you want to store, and your budget. As you may have guessed, a smaller rain barrel will cost less than a larger barrel.
To determine how large your catchment area is, go to GoogleEarth and zoom into your house. Then trace the area of the roof that will drain to the downspout you have chosen for your rain barrel. Imagine where a drop of rain would go if it fell on your roof. The image below is an example of this exercise.
Designers typically size rainwater cisterns to 1 inch of rainfall. To determine the volume your rain barrel needs to be, multiply your catchment area by 0.62. In the example shown in the image above, I would need a rain barrel that is about 150 gallons in size to capture the rainfall from the roof. However, someone may not want to install a rain barrel that large in their backyard. In this case, they would install an overflow system to prevent large messes during a larger rainfall event.
A general rule of thumb to use when sizing rain barrels is that 1 inch of rainfall on a catchment area of 100 square feet results in 62.3 gallons of volume. For example, a 55-gallon barrel would provide storage for a catchment area that is 90 square feet. You can still use a smaller rain barrel size as long as you install an overflow system.
Overflow System For Your Rain Barrel
An overflow system will prevent excess water from pooling up around your rain barrel and possibly damaging your home’s foundation. Overflow systems do not need to be complicated or expensive. A system like the one shown in the image below would work well.
The video below also explains how to set up a rain barrel overflow hose.
In addition to installing an overflow system, there are a few things you can do to prevent your rain barrel from overflowing during a large storm:
- Empty your rain barrel before the storm.
- Hook up a hose to the spigot and put the hose somewhere away from your home or other structures. Ideally, you want to put the hose in a sport where water will flow to a ditch or well-draining spot on your lawn.
- Clean your gutters to make sure leaves and debris will not clog up your rain barrel.
Material of the Rain Barrel
The material your rain barrel is made out of should block light to minimize the amount of algae growth in your tank. This means your rain barrel should be made of an opaque material.
Plastic rain barrels are probably the most popular type of rain barrel. One reason for this is that they are more affordable than rain barrels made from metal, wood, or ceramic.
Metal, wood, and ceramic rain barrels are sometimes installed for aesthetic purposes. I would recommend avoiding metal barrels because they tend to rust.
Do You Need A Pump For A Rain Barrel?
Gravity flow from a rain barrel is sufficient for filling up a bucket or watering can to water nearby garden beds. If you want to use your rain barrel to water plants with a hose or for another purpose, you will need a pump in order to provide enough pressure. The table below summarizes the specifications you should be looking for when purchasing a pump.
| Purpose of Rain Barrel | Pressure (psi) | Flow (gph) |
|---|---|---|
| Garden hose | 35 | 300 |
| Sprinkler | 40 | 270 |
| Pressure Washer | 20 | 240 |
Cost Of A Rain Barrel
In general, a rain barrel will cost between $100 and $200 depending on whether you build the system yourself. The most economical rain barrels cost between $80 and $100 at big box stores and Amazon. There are some more high-end systems available that cost between $230 and $400. These high-end rain barrels tend to be more aesthetically pleasing. In addition to the rain barrel itself, you may need some additional items. An example cost breakdown is shown in the table below.
| Item | Cost |
|---|---|
| Rain Barrel | $100 |
| Overflow Hose | $20 |
| Hacksaw To Cut Downspout | $10 |
| Leveling Sand (Optional) | $10 |
| Flexible Downspout Adapter | $10 |
| Bricks or Cinder Blocks To Elevate The Rain Barrel (Optional) | $8 |
| Pump To Increase Water Pressure (Optional) | $25 |
| Nylon Strap To Secure Rain Barrel | $17 |
| TOTAL | $200 |
In some cases, you may be able to get a 55-gallon barrel for free to make your own system. There are also many other items in the table above that you may be able to get for free.
Installing The Rain Barrel
After selecting the right rain barrel for your situation, it is important to correctly install the rain barrel in order for the system to work properly.
Step 1: Create A Smooth Surface For Rain Barrel
Before placing the rain barrel near a downspout, it is important to create a stable base for the rain barrel. Remove any grass, rocks, or grass around the base of the rain barrel. The level the soil and add a couple of inches of leveling sand if necessary. Finally, elevate the rain barrel using cinder blocks or bricks. Elevating your rain barrel will make it easier to access the spigot in order to fill up a watering can.
Step 2: Cut the Downspout
Place the rain barrel on top of the base your prepared in Step 1. Then mark a spot on the downspout that is 9-12 inches above the top of the barrel. Finally, use a hacksaw to cut through the downspout.
Source: North Carolina State University Rain Barrel How-To
Step 3: Attach Downspout Connectors
Install downspout connectors to connect the metal gutter material to flexible downspout. You can either purchase downspout connectors from the hardware store or fashion one from leftover downspout material.
Step 4: Connect The Overflow Hose
Then connect the overflow hose. Direct the overflow hose away from your home such that standing water will not adversely impact the structure. If possible, direct the overflow hose to a plant bed or to a dry spot on your lawn.
Step 5: Attach A Support Strap
Finally, use a strap to secure the rain barrel to a building or other sturdy structure. A support strap will prevent the rain barrel from tipping over in the event of a heavy storm or earthquake.
When securing a rain barrel, use nylon straps rather than metal straps. These types of straps are commonly sold at automotive stores or big box stores. It is particularly important to avoid using metal if you have a plastic rain barrel as metal-on-plastic is not a good idea.
Maintaining A Rain Barrel
Like most of the things that belong in your lawn and garden, rain barrels do require some maintenance. A diligent maintenance routine will significantly increase the life of your rain barrel and will allow the system to work more effectively. An unmaintained rain barrel can cause flooding in the vicinity of the rain barrel, cause insect problems, and cause a mess.
The table below outlines a good maintenance routine for a typical rain barrel.
| Maintenance Item | Frequency |
|---|---|
| Depending on where you live, you should disconnect your rain barrel and drain the water to avoid freeze/thaw damage. | Seasonal |
| Clean your gutters to avoid excess debris from getting into your rain barrel. | Quarterly |
| Empty your rain barrel and thoroughly clean the inside of the barrel with a non-toxic soap or cleaning agent. | Annually |
| Inspect your rain barrel for any cracks or other potential damage. | Monthly |
| Check your rain barrel for mosquitoes and see if you need to apply a mosquito control product like Mosquito Dunk | Weekly |