How Do Rain Barrels Work and Is Rain Harvesting Right for You? - Republic of Green

How Do Rain Barrels Work and Is Rain Harvesting Right for You?

Wondering if rain barrels are worth it and if rainwater collection could work well for you? Perhaps you are in one of states that has been suffering drought conditions, or perhaps you’ve got torrents of rain coming down and would just like to capture some of it to save money on your water bill. In either case, rainwater collection, by the simple means of using your downspouts and a rain barrel to capture rainwater, can be a very simple solution.  Rainwater harvesting has become much more popular in recent years, with many types of rainwater collection systems and decorative rain barrels now available.

In this overview, we will take an in-depth look at how rain barrels work, whether rainwater harvesting is legal in your state, how you can set up your own rainwater harvesting system, the benefits of rain barrels, one potential problem with rain barrels, and finally, we’ll end with our top picks for rain barrels to help you get started.

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Water Use Statistics 

First, let’s look at a few eye-opening water facts:

  • The average American family uses more than 300 gallons of water per day at home, according to the EPA, with approximately 30% of that used outdoors, or up to 60% in arid regions. Up to 50% of water used outdoors is lost to evaporation and run-off.
  • The average U.S. household spends more than $1000 per year on their water bill, according to the EPA.
  • Over 55 percent of the lower 48 states in the U.S. were in drought as of December 2022, according to the U.S. Drought Monitor.
  • By 2025, two-thirds of the world’s population may face serious water shortages, according to the Worldwide Wildlife Fund (WWF).

Obviously, water is a precious resource. If you are in a drought-prone area, you will be especially aware of how much water you use. And, if you’ve watched rain finally come and then have all of your gutter water just run off of your property, you might be wondering how to capture and use that precious water instead.

Installing rain barrels to collect rainwater from your downspouts is a simple way that you can reduce the water footprint of your household by using rainwater instead of tap water for non-potable purposes such as landscape watering. You’ll reduce your water bill, and help conserve water for the planet too!

Where does rain normally go when it falls?

First, let’s take a look at what happens when rain falls onto your property. Ideally, rain falls onto your yard, waters your landscape, and soaks into the ground, right where it fell. That is healthy and optimal. However, when heavy rain falls onto your roof and then is directed into your gutters and downspout, the resulting gush of water that comes out of your downspout cannot all be absorbed and thus it runs away if there is a direction for it to go — downhill across your property, or to the street gutter where it eventually makes its way into a stormwater drainage system. Unfortunately, stormwater runoff picks up contaminants from roofs, lawns, driveways, and streets that are carried into the drainage system which can then pollute surrounding waterways. If you live on a hill, that rushing water can also cause erosion or even instability in the soil.

Given the amount of expensive tap water that is used to water your lawn, and the downside of rainwater runoff, it seems a shame to let all that rainwater from the roof leave your property when it could be collected and put to good use for your own landscape. Hence, the increasing popularity of rain barrels as a way to collect and store rainwater for future use.

How Do Rain Barrels Work?

FCMP Outdoor RC4000 50-Gallon

Now, let’s get into how rainwater collection actually works.

Depending on the availability of rainwater in your area and your watering needs (e.g. small yard with drought tolerant plants vs large yard with extensive garden) you might opt for a single decorative rain barrel or multiple rain barrels that form a rainwater harvesting system.

The basic concept is that rainwater is collected from your rooftop by connecting a diverter to your gutter downspout which then sends that water into a rain barrel, where it is stored. Placing the barrel on a rain barrel stand will give it some elevation necessary to create water pressure, or you can install a pump. A spigot and garden hose are then connected for distributing the water for your intended use.

The water collected in your rain barrels can be used for irrigating your lawn or ornamental (non-edible) plants, washing your car, or other outdoor uses. Less commonly, and you’ll need to check if your state regulations allow it, harvested rainwater can be pumped back into the home for certain approved uses, such as flushing toilets. Rainwater should never be used for drinking.

What are the components needed for a Rain Harvesting System?

There are a few component parts to creating your rainwater collection system.

Rainwater barrels are obviously the most important part of any rain harvesting system as having a place to store the water is the fundamental part of the system. Most rain barrels are 50-gallon drums and are made from plastic; however, they are also available in various sizes and materials like metal, wood or terra cotta.

You will also need a way to effectively move that water from the roof to the rain barrels, a filtering system that keeps out debris and other foreign objects, and a distribution system that allows you to move that stored water to other parts of your property (for outdoor irrigation use), or, less commonly, to your home (for approved non-potable indoor use).

The different components of a rain barrel collection system include:

  • Gutters: Rain barrels can be connected to almost every type of existing gutter and downspout system.
  • A downspout diverter: This is essentially a gutter accessory installed on your downspout that allows you to route rainwater runoff into a rain barrel.
  • A spigot: In the simplest of iterations, you will need a spigot that can be connected (with the necessary couplings) to the rain barrel. To this spigot, you can then connect a simple garden soaker hose for easy irrigation of nearby garden plants.
  • Filter/Grate: It is also important to ensure that the water coming off your roof does not bring with it dust, debris, and other organic material that may accumulate on your roof and in your gutters. A filter and/or grate system can be placed at the end of the downspout to keep your rain barrels clean. This simple rain barrel screen sold on Amazon can be easily connected to your downspout where it enters your rain barrel.
  • First flush diverter: Another way to ensure that your rain barrels are not contaminated with debris is to install a first flush diverter. This device connects to your downspout, and diverts the first flush of rain water before it goes to your tank. Since the “first flush” of rainwater will generally clean your roof of the accumulated dust and debris, this device can be an important part of the system to ensure the cleanest possible water. This first flush diverter even allows you to use your diverted water as the first flush is automatically released through the slow release valve. You can empty this water into a standard drip irrigation system for use around your garden or you can direct it into storm water drainage.
  • Pump: A rain barrel pump will provide the water pressure needed to move your rainwater to the garden or wherever you want it to go. A 1/3 horsepower sump pump is one recommendation. The other alternative is to let gravity do the work by putting the barrel on a rain barrel stand or at a higher place on your property. Depending on your desired use, though can be difficult to get the elevation needed to achieved the desired water pressure, and thus a pump is a more reliable solution.
  • Overflow diverter: Lastly, you also need to have some sort of system that diverts overflow from your rain barrels. During heavy rains and long periods of rainy weather, you may accumulate more rain water in your barrels than you can use. An overflow diverter connects to the top of your rain barrels and moves that water to another part of your property. Some people choose to divert the overflow to the storm water or sewer system, or to a constructed wetland on their property.


Benefits of Rain Barrels

The benefits of rainwater collection are numerous.

  • Rainwater harvesting reduces your need to use potable water for non-potable purposes such as landscape irrigation and thus will reduce your water bill. Many sources quote the EPA as saying that homeowners could save as much as 1,300 gallons of water during the summer months, but I have not been able to locate the original research on that and the estimate may be for geographic areas where it rains a lot during the summer.
  • Your reduced water usage will help conserve your local reservoir. With many states experiencing drought, every bit of water conservation counts.
  • Rain catchment can reduce erosion and sediment run-off from your property.
  • Collection of rainwater on-site means that your local water utility can save money and conserve energy by not needing to send as much of the municipal water supply to your house.
  • Rainwater is considered “soft water” that does not contain any chlorine, lime or calcium, which are often present in the public water delivered to your home. This makes rainwater gentler for watering your ornamental plants and washing your car.
  • Rain barrel systems divert rain water from storm drains and sewer systems. Because storm sewers are often overburdened during major rain events, rain barrels can help to decrease the impact of runoff to streams and other parts of the watershed. Stormwater runoff often contains fertilizers, pesticides and other contaminants that flow into local waterways and harm wildlife.

Is it illegal to collect rainwater in your state?

Before you start shopping for rain barrels, you should first check if there are any restrictions on rainwater harvesting that apply in your state. Most states have no regulations, other states do have some regulations or restrictions, and some states, with or without restrictions, actively encourage you to collect rainwater.

Regulations or restrictions vary by state, but include things like the water must be used for outside or approved uses, or there is a limit on the number of gallons that can be collected.

Rainwater collection laws by state:

No Regulations AND It’s Encouraged: Maryland, Connecticut, Delaware, Florida, Hawaii, Indiana, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Dakota, Pennsylvania, Rhode Island, South Carolina

No Regulations or Restrictions: Alabama, Alaska, Arizona, Iowa, Kansas, Kentucky, Maine, Mississippi, Oklahoma, South Dakota, Tennessee, Vermont, West Virginia, Wisconsin, Wyoming

Some Regulations AND It’s Encouraged: Texas, Virginia

Some Regulations or Restrictions: Arkansas, California, Colorado, Georgia, Idaho, Illinois, Louisiana, Nevada, North Carolina, Ohio, Oregon, Utah, Washington

Visit What are the State Regulations on Rainwater Harvesting for more details on your state.


How clean is harvested rainwater and what can it be used for?

Rainwater is generally clean enough to use for non-potable outdoor purposes, which we will detail below. However, the water cleanliness is something that you can help manage by how you collect and store it, and the water quality can change over time.

Rainwater purity may be impacted by various things along its journey into your water storage barrel. It’s possible that rainwater in the sky may pick up elements of air pollution. Once it lands on your roof, rainwater runoff may pick up debris or contaminants like bird poop, bacteria, parasites, or chemicals, according to the CDC. Once it is stored in your rain barrel, if you leave it in too long, it may grow algae or start breeding mosquitoes. So, these are all things to be aware of so that you can use best practices to keep your rainwater as clean as possible.

What can harvested rainwater be used for?

First off, rain barrel water is for non-potable use only. It should not be used as drinking water, nor to wash food, or irrigate edible plants. It is best used for watering lawns and ornamental plants. You could also use it to wash your car.  If you set up a system to bring the rainwater indoors, you could use it to flush toilets, or, some sources suggest that you could use rainwater for laundry or bathing. However, for any indoor uses you’d want to check your local plumbing codes and rainwater regulations to make sure it is allowed.

How long can you store rainwater and what happens if you store it too long? 

Rainwater can be stored for anywhere from one week to indefinitely, depending on the conditions in which it is stored and how you plan to use the collected water.

Many sources suggest that stored rainwater can start to get contaminated after one week unless precautions are taken. Without proper management, the stored rainwater can start to grow algae, or bugs could get into the barrel and decompose, or mosquitos could start to breed.

To keep your water clean, use screens and first flush diverters to prevent debris from getting into the barrel and keep the barrel out of direct sunlight (and paint it opaque) to help to prevent algae growth. For longer storage, it is recommended to treat the water with a very weak bleach solution to clean it before using.

Note: If you live in an area that freezes in the winter, you’ll need to winterize your rain barrel and empty it from water that could freeze and crack your barrel. One simple way to winterize your barrel is to turn the barrel upside down and drain completely and move the barrel into a garage or shed. For larger and heavier barrels, you can also drain completely and divert the downspout to your regular sewer system.

How do you clean rain barrels?

Any time you notice debris inside your rain barrel or the presence of algae, it is a good idea to clean the barrels. Simply disconnect the downspout from the area where it enters the rain barrel, lay the barrel on its side and thoroughly spray rinse the interior. You can also use a brush to scrub the interior. A mixture of vinegar and water can help to clean the sides of algae buildup.

Do Rain Barrels Make Financial Sense?

While rain barrels make environmental sense, you’re probably curious if they make financial sense too. That will depend in part on how much it rains in your area, how much rainwater you are able to collect based on your roof size and slant, and how much potable water use you are able to offset. So the answer will be individual to you.

These are some rough estimates, but let’s assume that 2-barrel system with all of the required parts might cost between $100-$600, depending on how much you DIY. Per the EPA, the average household spends at least $1000 per year on water with 30-60% of that spent on outdoor water use. The outdoor water number varies greatly based on state, size and type of landscaping, water features, etc. If you are able to replace ALL of your outdoor watering with rainwater, your payback period might be anywhere between one and six years. You likely won’t replace all of your outdoor water use with rainwater, but that’s a rough idea of how to look at it. Then, since most rain barrels last for a decade with minimal need for repair or maintenance, you’ll be in the money once you hit break even.

What Size Rain Barrels Do I Need?

Most people are genuinely surprised at the amount of rain water that they can harvest from their roof. For example, a 1,360 square foot roof on a house that gets an average of 10-inches of rain over the course of the spring and summer would be able to collects around 8,160 gallons of rainwater. Even if you irrigate your lawn regularly, this amount of free water can help to drastically reduce your overall water consumption.

There are a number of simple rain water calculators that can help you determine how much rain water you can potentially collect. Simply add the dimensions of your roof and the estimated amount of average rainfall to discover how much water you can save.

Potential Problems with Rain Barrels

While collecting rainwater can be a great thing, collecting too much of it without a way to divert overflow can be a bad thing. Due to their small size, many rain barrels are simply unable to store the vast amount of water that might fall during a heavy rain. During a strong storm, your roof may accumulate thousands of gallons of water. Unless you have implemented a way for overflow water to be diverted, overflowing rain barrels could lead to water in your basement or crawl space or moisture issues for a slab. So, make sure to ensure proper overflow diversion to keep excess water away from your home.

What are Rain Barrels Made Of? 

Rain barrels are made out of a variety of materials, including plastic, wood, metal, and terra cotta, each with their pros and cons. Some rain barrels are purely functional, while others aspire to look good too. Here are commonly used materials and their characteristics:

Good Ideas RW50-OAK Rain Wizard Rain Barrel 50 Gallon, Oak

  • Plastic rain barrels: These are generally the cheapest options on the market, and when placed correctly can last for decades with minimal maintenance. Due to their lack of aesthetic qualities, however, many people may choose to “hide” these barrels as much as possible.
  • Wood rain barrels: These barrels can offer a beautiful addition to the façade of your home. They are also sturdy and will not be affected by heavy winds. However, you will need to use a strong wood preservative in order to prolong the lifespan of these barrel options.
  • Metal rain barrels: Most metal rain barrels on the market today are made of sturdy corrugated galvanized steel metal dunked in hot zinc. These metal rain barrels will not rust, are fairly lightweight for transporting and setting up, and also come in several sizes. As a word of caution, you should be wary of using old or recycled metal tanks because they may contain lead.
  • Terra cotta rain barrels: Terra cotta rain barrels are made from fired clay (ceramic). As a natural material, they are one of the most “ecological” options, and can offer a stunning appearance for your home. They can also combine with other terra cotta planters that you locate throughout your landscape. Terra cotta rain barrels will crack or break if tipped over, and special care needs to be taken when cleaning. Also, terra cotta rain barrels should also be placed on top of a foundation that keeps them away from the soil. Prolonged exposure to soil moisture can cause moss to grow on the terra cotta surface.

How to hide rain barrels: If you would like to hide your rain barrels from view, you could re-route your gutter system so that the downspout runs to a back corner of your home out of sight from the main road or entranceway to your home. You could also camouflage your rain barrels with vegetation.


Our Picks: Best Rain Barrels for Rainwater Harvesting

If you are ready to start storing your rainwater, where you can go to find the best rain barrels? Though some handy DIY homeowners may want to design their own customized rain barrels, others may look for turnkey solutions. Below, we offer a few suggestions for the best rain barrels you can purchase ready-to-use to get up and running quickly:


FCMP Outdoor Rain Barrel System: This simple 50-gallon heavy-duty outdoor home rain catcher barrel water comes with a connected spigot and a mesh screen for a filter.

Good Ideas RW50-OAK Rain Wizard Rain Barrel 50 Gallon, Oak – This 50-gallon faux wood rain barrel is made of polyethylene resin that won’t rot or crack. It includes a brass spigot.

EarthMinded RainStation 45 Gal. Recycled Black Rain Barrel with Diverter – This decorative rain barrel has a sealed system that resists mosquitoes, insects and algae growth. Includes diverter and all parts needed for installation.

Looking for more decorative rain barrels? Amazon has wide selection to choose from, including rain barrels with planters on top.

Go Out and Save Water

No matter what type of rain barrel you choose, we hope you’ll have fun and gain some real satisfaction from collecting rainwater, conserving water, and reducing your water bill. Please let us know your experiences in the comments below!

Main top image: Good Ideas 50 Gallons Gal. Plastic Drainable Planter Rain Barrel sold on Wayfair.

Tobias Roberts

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