What Is Rainwater Harvesting? 12 Things (2024) You Must Know

Rainwater harvesting — the collection and storage of rain to use as a primary water supply — is one of the simplest and oldest methods of self-water supply.

And it’s still a great one.

Rainwater is the cleanest form of water on the planet.

While you’ll still need to filter it before use, learning how to harvest rainwater has numerous benefits.

In this blog, we’ll tell you everything you need to know about this cheap and sustainable system.

Let’s get started.

1. What is rainwater harvesting (RWH)?

Rainwater harvesting is the collection and storage of rain for use.

RWH often involves harvesting rain from a roof.

As the water is channeled into downspouts, it can be directly transferred into rain barrels or other collection containers.

Rainwater harvesting is a viable alternative for anyone looking to supply their household or business with water.

While it’s traditionally thought of as something that homesteaders do, anyone can use these methods and reap the rewards.

You may also hear it referred to as rainwater collection, rainwater catchment, roof water collection, or rooftop water collection.

RWH is a viable technology in both urban, suburban, and rural settings.

It provides you with the ability to take advantage of a free water source and can be configured to supply your entire house or landscaping needs.

2. Is rainwater clean?

If you’ve never harvested rainwater previously, you may worry if it’s clean.

Is it safe to drink?

Will it make me sick?

The answer all depends on where it’s coming from.

In general, most rainwater is safe as long as you don’t drink it near chemical plants and areas of high pollution.

However, the general recommendation is that you filter it before you drink.

Another way to make the rainwater safer is to boil it to make sure you’re killing off any pollen or bacteria that may be lingering in the water.

Boiling it is a good step if you want to use it for non-consumption purposes, but we still recommend going the extra step of filtration to ensure you have clean water.

3. Is rainwater harvesting legal?

As you begin your research, you may hear some horror stories about people facing legal consequences for harvesting rainwater.

This will leave you with the question: Is it legal?

Yes, it is legal.

There are no federal laws that restrict rainwater harvesting, and while some states have strict regulations, most states will allow their residents to collect rainwater freely.

4. What types of regulations and restrictions do states have?

Some states have regulations about the amount of rainwater one can collect as well as how you can collect it.

That said, most states allow their citizens to collect rainwater freely and even encourage its collection.

The states with regulations believe that the collection of rainwater may halt the rainfall’s natural flow into the Earth’s aquifers and streams.

Thus, it will disrupt the hydrologic cycle.

However, a study published in the Scientific World Journal states that the amount of rainwater collected by individual homes would have little to no impact on the overall hydrological cycle.

As most of the collected rainwater would be used for gardening and household purposes, the water would eventually be returned to the ground.

And then sometimes states also restrict rainwater usage because of old prior appropriation laws.

Today, most states have shifted their laws in favor of private RWH.

Utah and Colorado are the only states with heavy regulation, and Colorado is the strictest of the two.

In 2016, they passed a bill that allows for the collection of rainwater with a 110-gallon maximum capacity.

See the next section for more information about the restrictions and regulations in each state.

So, remember, rainwater is a resource.

Once it falls on your property, it’s generally yours to use without restriction.

Organizations like the American Rainwater Catchment Systems Association (ARCSA) are generally working with government organizations to advocate for rain harvesters all over the country.

5. What is a state-by-state guide to rainwater harvesting?

Are you still worried about the possible restrictions in your state?

If so, we put together a state-by-state guide to help you understand any restrictions or regulations in your local area.

bulletAlabama – No regulations or laws against rainwater harvesting

bulletAlaska – No regulations or laws against rainwater harvesting

bulletArizona – Regulated through the Department of Water Resources; city or town may provide money to fund rainwater harvesting systems

bulletArkansas – Regulated through the State Board of Health, which allows a system used for nonpotable water that complies with the Arkansas Plumbing Code and is designed by a professional engineer

bulletCalifornia – Regulated through the Division of Water Rights, which includes specific system requirements and licensing criteria that landscapers must follow to install rainwater harvesting systems

bulletColorado – Each house is allowed a rain barrel of up to 110 gallons for storing rainwater

bulletConnecticut – No regulations or laws against rainwater harvesting

bulletDelaware – No regulations or laws against rainwater harvesting

bulletFlorida – No regulations or laws against rainwater harvesting

bulletGeorgia – The Department of Natural Resources, Environmental Protection Division regulates water resources; state plumbing code allows rainwater harvesting for outdoor use

bulletHawaii – No regulations or laws against rainwater harvesting

bulletIdaho – Legal to capture rainwater off roof structures and the ground if the rain has not entered a natural waterway

bulletIllinois – Local government can regulate rainwater harvesting per state plumbing law; rainwater can only be used for nonpotable uses

bulletIndiana – No regulations or laws against rainwater harvesting

bulletIowa – No regulations or laws against rainwater harvesting

bulletKansas – No regulations or laws against rainwater harvesting

bulletKentucky – No regulations or laws against rainwater harvesting

bulletLouisiana – No regulations or laws against rainwater harvesting

bulletMaine – No regulations or laws against rainwater harvesting

bulletMaryland – No regulations or laws against rainwater harvesting

bulletMassachusetts – No regulations or laws against rainwater harvesting

bulletMichigan – No regulations or laws against rainwater harvesting

bulletMinnesota – Regulated through the Minnesota Plumbing Board, which requires permitting and code compliance

bulletMississippi – No regulations or laws against rainwater harvesting

bulletMissouri – No regulations or laws against rainwater harvesting

bulletMontana – No regulations or laws against rainwater harvesting

bulletNebraska – No regulations or laws against rainwater harvesting

bulletNevada – Residents are allowed to collect rainwater off of a single-family roof for non-potable domestic use

bulletNew Hampshire – No regulations or laws against rainwater harvesting

bulletNew Jersey – No regulations or laws against rainwater harvesting

bulletNew Mexico – Regulated through the State Engineer Office; no specific requirements exist for outdoor uses; indoor uses must meet water quality standards

bulletNew York – No regulations or laws against rainwater harvesting

bulletNorth Carolina – Rainwater harvesting is encouraged due to water conservation efforts

bulletNorth Dakota – No regulations or laws against rainwater harvesting

bulletOhio – Rainwater harvesting is legal, but there are codes and regulations that must be followed

bulletOklahoma – Encouraged through state legislation: Water for 2060 Act

bulletOregon – Rainwater harvesting is legal, but only using rooftop surface water

bulletPennsylvania – No regulations or laws against rainwater harvesting

bulletRhode Island – No regulations or laws against rainwater harvesting

bulletSouth Carolina – No regulations or laws against rainwater harvesting

bulletSouth Dakota – No regulations or laws against rainwater harvesting

bulletTennessee – No regulations or laws against rainwater harvesting.

bulletTexas – Highly encouraged. Some counties even offer a tax incentive. And there is an exemption on sales tax for rainwater harvesting systems

bulletUtah – 2,500 gallons max for rainwater harvesting systems. A permit is required

bulletVermont – Regulated through the Department of Environmental Conservation – 2017 Vermont Stormwater Management Manual Rule

bulletVirginia – Regulated through state legislature and state plumbing code

bulletWashington – No regulations or laws against rainwater harvesting

bulletWest Virginia – No regulations or laws against rainwater harvesting

bulletWisconsin – No regulations or laws against rainwater harvesting

bulletWyoming – No regulations or laws against rainwater harvesting

6. What are the benefits of rainwater collection?

Rainwater harvesting has a variety of benefits, which is why it’s becoming increasingly more popular.

These include:

bulletIt’s relatively clean

bulletIt’s a free source of water

bulletIt’s socially acceptable and environmentally responsible

bulletIt promotes self-sufficiency

bulletIt helps conserve water

bulletIt’s better for landscape irrigation and gardens because it isn’t chlorinated

bulletIt reduces stormwater runoff from homes and businesses

bulletIt helps solve drainage problems on your property while providing you with free water

bulletIt utilizes simple technologies that are inexpensive and easy to maintain

bulletIt can be used as the main source of water or backup source of water for wells and municipal water

bulletIt allows for a system that can be easily retrofitted to an existing structure or built during a new home construction

bulletIts system is flexible and can be modular, allowing expansion, reconfiguration, or relocation (if necessary)

bulletIt can provide an excellent emergency source of water

bulletIt is sodium-free, which is important for persons on low-sodium diets

7. What are the uses for harvested rainwater?

Rainwater can be used in almost all the same ways that other water supplies are used (i.e., well, etc.).

If you intend to use the water for drinking, food preparation, and other direct human consumption, then you’ll need to filter the water to remove pathogens, grit, and other particles.

If you’re not able to filter it, we recommend boiling it at a rolling boil for at least one minute to kill disease-causing organisms.

Here are the top uses for rainwater (with necessary filtration in mind):

bulletOutdoor Uses

  1. Garden and landscaping
  2. Swimming pools
  3. Livestock water
  4. Household chores like car or dog washing
  5. Water features like birdbaths or fountains
  6. Fire suppression or emergency water

bulletIndoor Uses

  1. Washing machine
  2. Dishwasher
  3. Hot tub, bath, or shower
  4. Toilet
  5. Utility sink

9. Why is rainwater harvesting important?

Rainwater harvesting is important because it’s one of the best ways we can conserve water.

Water conservation gains have largely been achieved inside our homes, so we need to start looking for ways that we can conserve water outdoors as well.

Rainwater harvesting is a major way we can do this…it’s time we all start looking at implementing this!

10. How much rain can you collect?

The amount of rainfall you can collect is governed by the following formula:

1″ of rain x 1 sq. ft. = 0.623 gallons

The easiest way to remember this formula is by remembering that 1 inch of rainfall over 1,000 square feet will yield 623 gallons.

To calculate the amount of rainwater you can collect, you need to know the annual average precipitation for your area.

We recommend looking at the NCDC Monthly Precipitation Probabilities and Quintiles.

Once you find the closest weather station to you, use the 0.5 row to determine your annual average precipitation.

Then, use a rainwater collection calculator to determine your total rainwater collection potential using those values.

11. What are the different methods for collecting rainwater?

There are a few different methods for harvesting rainwater.

Here are the most common methods if you’re interested in getting started.

bulletRain barrels

This method is the most common.

It involves installing a barrel at a gutter downspout to collect rainwater.

The actual barrel may be a recycled barrel or a new commercially available rain barrel.

The pros to this system are that it is easily implemented by anyone with a residence and that barrels are readily available in your community.

Additionally, the barrels don’t take up much space, and they can fit into any situation.

The cons are that the capacity of the barrels is only 50 to 100 gallons, and the barrels can easily overflow.

bullet“Dry” system

This system is a variation of a rain barrel setup.

It involves a larger storage volume, which means the collection pipe “dries” after each rain event as it empties directly into the top of the tank.

The pros of the “dry” system are that it can store a large amount of rainwater, and it’s less expensive to implement.

It’s also great for climates where rainfall happens with infrequent, larger storm events, and it’s a less complicated system to maintain.

The con of the “dry system” includes the fact that the storage tank must be located next to your house.

bullet“Wet” system

This system involves locating the collection pipes underground to connect multiple downspouts from different gutters.

The rainwater will fill the underground piping, and the water will rise in the vertical pipes until it spills into the tank.

The downspout and underground collection piping must have a water-tight connection in order for this to work.

The elevation of the tank inlet should also be the lowest gutter on the house.

Some pros of this system include having the ability to collect water from your entire collection surface and having the ability to collect from multiple gutters and downspouts.

The tank can also be located away from your house.

Some cons of this system include the fact that it’s more expensive to implement because of the underground piping.

12. What are the components of a complete rainwater collection system?

For a complete rainwater collections system, here are the features you’ll need:

bulletRoof surface: Make sure you have a roof surface suitable for rainwater harvesting

bulletGutter protection screening: Helps to keep large debris from entering your gutters

bulletGutter: You can collect rainwater from any type and shape of gutter

bulletRain head: This is an additional filtration opportunity

bulletFirst-flusher diverter: This helps prevent the first flush of contaminated rainwater from entering the tank

bulletTank screen: This is installed on the tank entry point to keep mosquitos and pests out

bulletRainwater tanks: These come in all shapes and sizes to hold your rainwater

bulletInsect proof flap valve: This element of your rainwater system keeps mosquitos and pests out

bulletAuto-fill system: This is installed to always keep a minimum amount of water in the tank

bulletPump system: This provides pressurized rainwater to distribute the rainwater or connect to an irrigation system

bulletIrrigation filter: This helps you catch any large debris that may have gotten through the pump

bulletWater level indicator: This can be helpful in monitoring the water usage from the tank

Final Thoughts

If you’re interested in using rainwater harvesting as a source of water, get started today!

You’re merely harnessing a free water source that would otherwise go unused.

Use our tips above to help you create the system of your dreams.

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Erika Gokce Capital

Disclaimer: we are not lawyers, accountants or financial advisors and the information in this article is for informational purposes only. This article is based on our own research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.


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