How to Conserve Water at Home with a Rainwater Harvesting System

Posted by
John Woodard on October 13, 2023

As environmental consciousness becomes more common, you may wonder how you can make environmentally friendly choices with your water use at home. Rainwater harvesting provides an excellent opportunity to benefit the environment while also having positive effects around your home. With very little downside, rainwater collection is a great way to conserve water and lower your water bill. In this article, you can learn about what rainwater harvesting is, the parts of a rainwater collection system, and how rainwater can be used in and around your home.

What is rainwater harvesting?

Rainwater harvesting is the process of catching, filtering, and collecting water to conserve it for later use. The water is collected from rooftops, where it flows down to the gutters, through downspouts, and into a collection tank. These storage tanks take on many sizes, and they can be installed above ground or beneath your yard. They can be connected to hoses that you can use on your lawn, filtration systems that pipe into your house, or other systems where the water can be used as needed.

What are the benefits of rainwater harvesting?

Rainwater harvesting provides many benefits to your home, your wallet, and the environment.

  • Can save you money on your water bill. Rainwater is an excellent tap water alternative for water-heavy outdoor uses, such as washing cars and gardening. This rainwater can save you money each month on your water bill, allowing your rainwater harvesting system to pay for itself over time.
  • Benefits the environment. Rainwater runoff contributes to soil erosion, a phenomenon that disrupts ecosystems and compromises the ability to grow crops. By collecting rainwater before it becomes runoff, you can curb the effects of soil erosion.
  • Better than tap water for certain uses. While stored rainwater is not potable without filtration, it is better for certain applications than tap water. For example, the chlorine in tap water can eat away at your car’s paint and kill beneficial bacteria in soil. Rainwater, on the other hand, does not contain the treatment chemicals that tap water possesses. As a result, rainwater is better for washing cars and gardening than tap water.
  • Can provide water during times of drought. If you live in a drought-prone region, collecting rainwater can provide additional water when restrictions are put in place. When connected to appropriate water treatment systems, rainwater can be used for potable applications inside the home.

Learn more: 5 advantages of rainwater harvesting

What are the downsides of rainwater harvesting?

While rainwater harvesting has many advantages, there are a few disadvantages to consider.

  • Not legal everywhere. Some states or municipalities may limit the amount of rainwater you can collect or outlaw it altogether. There are currently no federal restrictions placed on rainwater harvesting, so contacting your local authorities is the best way to determine the rainwater collection regulations in your area.
  • Unpredictable rainfall. One of the biggest disadvantages of rainwater harvesting is the inconsistency of rainfall. If you rely on rainwater for gardening, washing your cars, or other applications, you may find yourself running out during times of drought.
  • Limited by tank size. Rainwater harvesting becomes more expensive when you wish to store large amounts of water at a time. For example, if you use a 50-gallon rain barrel and it becomes full, you will not be able to take advantage of the next rainfall. If you wish to opt for a larger tank, you will need to spend substantially more money.
  • Initial cost. Over time, rainwater harvesting can save you money on your water bill. However, the initial cost of a rain barrel and its components can turn people away from setting up a collection system at their homes.

Learn more: 5 disadvantages of rainwater harvesting

Types of rainwater harvesting systems

Rain barrels

Rain barrels are the most common and economical rainwater harvesting systems. A barrel is placed beneath a downspout and collects rain as it flows from a roof. Most rain barrels hold about 50 gallons of water. If the barrel has a spigot at its base, you can draw water directly from it, attach a hose, or link it to your irrigation system.

rain barrel with filter

Dry systems

Dry rainwater harvesting systems have larger storage volumes than rain barrels, but their premise is the same. A large tank is placed on your property and pipes run from your gutters into the tank, filling it with water every time it rains. They are called dry systems because the pipes dry out between rainfall events and fully empty into the tank thanks to gravity.

dry rainwater system

Wet systems

Wet rainwater harvesting systems differ from rain barrels and dry systems in that their piping is underground. When it rains, water flows down from gutters to underground pipes and then rises into a tank or fills an underground tank through a vertical pipe. They are called wet systems because the pipes constantly contain water and don’t dry out between rainfall events. Because of stagnant water in the pipes, wet systems are vulnerable to mosquito infestations and anaerobic fermentation. Therefore, it is recommended to screen the pipes and drain them periodically. While wet systems require a little more maintenance than rain barrels and dry systems, they are more aesthetically pleasing since the pipes are underground and the tank can be placed farther from your home.

What are the components of a rainwater harvesting system?

The components of a standard home rainwater harvesting system include a catchment surface, gutters, downspouts, first-flush diverter, storage container, and filters.

Catchment surface

The catchment surface is the area that rainwater initially falls onto. From here, the water flows to and collects in the gutters. In standard home rainwater collection systems, the home’s rooftop is the catchment surface. The larger the catchment surface, the more water will be collected from each rainfall. Because of this, homes with large rooftops should opt to include larger storage containers in their rainwater collection system.


The gutters receive water from the rooftop and divert it to the downspouts. You may hear the term “conveyance system” used for both the gutters and downspouts. This term simply means that they are moving water from one point to another.

Some homeowners may wish to filter out large chunks of debris before they enter the gutters. For this purpose, gutter guards are the most common and practical solution. Gutter guards cover the gutters with a mesh or strainer that prevents debris from flowing into the gutters and clogging the conveyance system.


The downspouts are the second stage of the conveyance system. They move water from the height of the rooftop to the level of the water storage container. They may also contain filters that catch debris before it can enter your rain barrel or other rainwater storage tank. A downspout filter is typically a strainer that can be installed at the top of or inside the downspout. If you do not protect your gutters with gutter guards, you will need to install downspout filters in your system. Even with gutter guards, a rainwater collection system can benefit from the use of downspout filters.

Learn more: Types of downspout filters

First-flush diverter

A first-flush diverter gets rid of the first water that flows through your collection system each rainfall. Debris, insects, feces, and other contaminants collect on your rooftop when rain is not falling. Once rain begins, all these contaminants wash into your gutters and downspouts. The first-flush diverter prevents the first bit of water from each rainfall from entering your water storage tank. This keeps the most contaminated water from polluting all the water in your storage tank.

Storage container

A rainwater storage container collects all rainwater that it receives and stores it for later use. A collection container can be stored above ground or underground, but most home collection systems use an above ground container. The most common types of above ground rain collection containers are cylindrical vessels called rain barrels. These containers are typically low-volume barrels that any homeowner can easily install. Compared to other storage containers, they are inexpensive and can be used for practically any home.

Learn more: What is a rain barrel and how does it work?

brown rain barrel

An underground water storage tank, unlike its above ground counterpart, is much more complicated to install and maintain. Because they are stored below a yard’s surface, underground tanks require extensive planning, expense, and digging to install. However, underground tanks are more weatherproof and can typically store larger volumes of water than above ground tanks. In many cases, septic tanks will be used for underground water storage because they already contain the specifications to lay underground for long periods of time.

Learn more: Above ground vs underground water storage tanks


Filters in a rainwater harvesting system can refer to downspout filters or conventional water filters that deliver water to your home. While downspout filters prevent large debris from entering your collection vessel, water filters can make your water cleaner for outdoor use or potable for indoor applications. To properly filter rainwater for potable uses, it must be disinfected and subsequently filtered.

Learn more: How to collect rainwater for drinking

Rainwater disinfection

Rainwater can potentially contain bacteria, viruses, parasites, and other microbiological contaminants that make it unsafe to drink. To prevent waterborne illnesses, rainwater must be disinfected with either a UV disinfection system or a water distiller.

A UV disinfection system deactivates microbiological contaminants with ultraviolet light. These systems are rated by the amount of water they disinfect per minute. While UV disinfection systems make water microbiologically safe, they do not filter out other contaminants. As a result, an appropriate filtration system following a UV system is essential. A sediment filter should also be used prior to the water running through the UV chamber.

Learn more: What is a UV water purifier and how does it work?

A water distiller can make rainwater potable by itself. Distillers purify water with the same method as the hydrological cycle. In this distillation process, water is heated until it evaporates. It then collects onto the ceiling of the distiller, where it cools down enough to condense into liquid. This liquid then drops into a collection container in the form of potable water. Unlike a UV system, a water distiller does not need to be followed up by a water filtration system.

Learn more: What is distilled water and is it safe to drink?

Rainwater filtration

After being disinfected by a UV system, rainwater must be filtered by an appropriate treatment system. The most common of these water filtration systems is reverse osmosis.

Reverse osmosis (RO) systems utilize a multi-stage treatment process to rid water of contaminants. These stages include a sediment filter, carbon filter, and an RO membrane. Many RO systems include additional stages, such as carbon and remineralization postfilters. RO systems reduce over 99% of contaminants in water, making it an ideal candidate for filtering rainwater.

Learn more: What is a reverse osmosis system and how does it work?

Do you need a pump for your rainwater harvesting system?

If you would like to use your harvested rainwater inside your home or away from the tank itself, then yes, you need a demand pump for your rainwater harvesting system. A water booster pump is a reliable, flow-based on demand pump that moves water from a storage tank to the intended point of use. A demand pump will pump water out of your rainwater harvesting system and provide the taps inside and outside of your home with pressurized flow. The other option is to simply use gravity to force the water from your tank, but this will limit how you can use your collected rainwater.

Learn More: What is a Demand Pump and How Does It Work? | What is a Water Booster Pump and How Does it Work?

Is it legal to collect rainwater?

It is not always legal to collect rainwater. Many states and municipalities have restrictions on rainwater harvesting systems and the amount of rainwater you may collect. For example, Colorado households are only allowed 110 gallons of rain barrel storage. Also, most states prohibit using harvested rainwater for drinking purposes. Rainwater harvesting is not regulated by federal law, so we recommend contacting your local authorities to determine if any restrictions are in place in your area.

Why is rainwater harvesting restricted?

Rainwater harvesting is restricted in some areas because harvested rainwater doesn’t go into nearby ponds, lakes, streams, and rivers, which has the potential to disrupt ecosystems. Additionally, rules against drinking harvested rainwater are in place for your safety. Without proper filtration, rainwater may contain harmful substances, such as bacteria and pesticides.

How much rainwater can I collect?

You can collect an abundance of rainwater each rainfall with even a small rooftop. According to the University of Arizona, a 1000-square-foot rooftop can collect 623 gallons of water for every inch of rainfall. The average annual rainfall in the contiguous United State is just above 30 inches. This means a home with a 1000-square-foot roof subjected to the average rainfall can collect as many as 18,690 inches of rainwater each year.

You can calculate how much rainwater you can collect at home with the following formula:

Gallons of rainwater collected per inch of rainfall = Area of rooftop (square feet) * 0.623

Where can I use harvested rainwater?

Harvested rainwater can be used in many outdoor and indoor applications. The outdoor uses for rainwater include washing cars, gardening, and watering your lawn. Because rainwater does not contain chlorine or chloramine like city-treated water does, it is more beneficial to use this water for these applications than tap water. Unlike indoor applications, outdoor rainwater applications do not require water to be disinfected to use safely.

hosing down car

Indoor uses for rainwater include toilet flushing, washing laundry, bathing, household cleaning, and drinking. Note that, before it can be used indoors, water must be disinfected and further treated before it is safe to use. If you only use rainwater to flush your toilets, it does not need to be treated. However, other uses, especially drinking, require thorough treatment.

Learn more: The 8 best uses for harvested rainwater | How to collect rainwater for drinking


If you have any additional questions, please do not hesitate to contact us.

No comments yet.
Leave a comment