Close-up of a spout on an old water tank

Rainwater Collection 101: Your Rain Harvesting Quick-Start Guide

The Gift of Rain: The Importance of Rainwater Collection

This article serves as an entry point to the exciting world of rainwater collection. Rainwater collection is nothing new; many people and cultures have practiced it for thousands of years. Just as the need for water hasn’t changed after all these years, the basic reasons people collect water remains very much the same. The bottom line is that people everywhere have always collected rainwater to provide themselves with greater security and ease in their daily lives.

This post will look at stormwater and rainwater collection systems. We will consider the similarities and differences between each. Next, we will explore a brief history of rainwater harvesting before discussing the benefits and limitations of this practice. Finally, we will look at Rainwater Management Solutions (RMS) and see how their unique program improves the collection process and reduces user maintenance. By the end of this post, you will have a good understanding of what rainwater collection is. And, if you are interested, you will know what steps to take to set up a system of your own. 

As a manufacturers representative of Rainwater Management Solutions, use their products as examples. Also, near the end of the article, we discuss their unique, maintenance-saving approach to rainwater collection so you can benefit from their experience and expertise.

Table of Contents

The Difference between Rainwater Collection and Stormwater Harvesting

Rainwater defined

Rainwater collection (also referred to as rainwater harvesting) is the process of collecting the free water that falls from the sky during rainfall. It is typically gathered on a collection surface and then directed into a tank or cistern. The water is captured before it hits the ground.  

Stormwater defined

In contrast, stormwater capture (also known as ‘stormwater harvesting and ‘stormwater collection’) refers to collecting water that has fallen on the ground. If water lands on a soft, natural surface like grass, it absorbs into the soil. When the soil is fully saturated, the water will pool together as surface runoff will find its way into a nearby lake or river.

When water comes into contact with hard surfaces (like asphalt and concrete), it has nowhere to go, so it begins to gather where it falls. This surface runoff becomes contaminated as it flows through concrete and asphalt surfaces in our urban environments. Therefore, this water is much dirtier than pure rainwater, and removing these pollutants becomes a more critical and complex task.

This image shows the effects of stormwater runoff in natural and urban environments.
This wonderful illustration from the Philadelphia Water Department illustrates natural vs. urban runoff

The History of Rainwater collection

Since all living things depend on water for survival, it is no surprise that humans have been collecting it ever since the dawn of civilization. As cities sprung up around the Indus, Tigres, Euphrates, and Nile Rivers thousands of years ago, people have sought to manage water. They dug wells and built cisterns, canals, and aqueducts. This control over water, coupled with the cultivation of farmland, gave people greater control over their well-being and allowed them to thrive.

In those days, people used the water much they do today- for drinking, cooking, irrigation, and washing. Complex collection systems were engineered in places where water was scarce to conserve as much as possible.

Sometimes, water collection was also a means of national security. For example, King Hezekiah of Israel had a massive tunnel dug to provide Jerusalem with water when the city was under siege. Have a look at this tunnel in the slideshow below, and check out other examples of ancient water collection systems:

  • Hezekiah's Tunnel
  • The beautiful Basilica Cistern in Instanbul Turkey
  • Medusa Head at the Basilica Cistern in Instanbul Turkey
  • Fortress Cistern, Golan Heights
  • The Portuguese Cistern in El-Jadida

Benefits of Collecting Rainwater and Stormwater

Money Savings

Unlike water from your municipal water system, rainwater is entirely free. Although there is an initial setup cost to harvest rainwater, you will find that using it will lower your monthly water bill.

Reduced Stress on Municipal Water Systems

Another benefit of using reclaimed water is that it helps ease the demand placed on water treatment plants. Creating potable water is a complex process that requires time and resources. By only using potable tap water for food preparation and washing, we help our systems operate efficiently.

Flood Management

Stormwater harvesting can be a great way to repurpose water and control flooding and erosion in areas where large amounts of water are present.


As stormwater runs along the ground and picks up contaminants, we reduce the number of pollutants that flow into our lakes and rivers by harvesting and filtering it.


Harvesting rainwater is a great way to lead by example. Using our resources wisely shows appreciation and respect for the natural design of our planet’s water cycle that sustains all life on Earth. Like our ancestors before us, we have a chance to play an active role in this story and pass this great legacy to future generations.

“We forget that the water cycle and the life cycle are one.”

Jacques Custeau

Limitations of Rainwater Collection Systems 

Poor Planning

Poor planning on the part of homeowners, DIYers, or the inexperienced can be very costly. Critical equipment can be left out, missized, or improperly installed. Not having a fundamental understanding of the rainfall in your area could lead to money wasted on a larger tank than is needed. Bad planning can be downright dangerous if it compromises water quality.

Water Quality

While rainfall itself is very clean, collecting and storing the water can often cause it to become contaminated. For example, if you harvest water from a dirty roof, the water may contact bird feces, dust, and dirt before entering the tank. (Gross!) This fact makes it critical for you to test the quality of your water. 

You might intend to use your harvested water for drinking and cooking (which the CDC does NOT recommend). We would advise against this. You are better off using your tap water for drinking and cooking while saving your reclaimed water for other uses. 

Initial Cost

People eager to install a rain water collection system might focus only on what great stewards they are and the money they will save on their water bills. But, they should also consider the initial investment they must make to purchase and install a system.

If this is you, you may be in for a shock regarding the setup cost. Costs can vary widely, depending on the size and scope of your project, but it is best to view your efforts as a long-term investment. There are no shortcuts, but you will eventually reap great benefits for your wallet and your planet tomorrow by taking informed action today.


A rain water collection system is not a “set-it-and-forget-it” effort. Even the best systems will require check-ups and care from time to time. The frequency of this occurrence greatly depends on the design of your system.

How Rainwater and Stormwater Collection Systems Work: Two common collection methods

An Honorary mention

Before we begin, there needs to be mention of the most straightforward rainwater collection system known to man: the ‘water butt.’ (We’re not making this up – go ahead and giggle. It’s British… And also known as the ‘rain-barrel method’ by more practitioners). This design is a simple bucket under a downspout; the water collected is typically used to water garden plants. There are two other categories of systems,0.0 however:

Dry Systems

The dry system collects water from a roof catchment area, using gutters and downspouts to pipe the water directly into the top of a collection tank. This setup allows the pipes will dry out after a rainfall. Because the system uses gravity, the tank needs to be near your catchment area.

The benefits of this system are that it is simple and, therefore, quicker and cheaper to build while requiring less maintenance. The tradeoff is that your collection tank must be very close to your building, which might not be possible in some scenarios.

Wet Systems

A wet system is a little more flexible than a dry system; the collection tank can be located anywhere on the property. Pipes run from the roof catchment area and go underground, below the level of the tank inlets. The water pipes always remain full of water. After a rainfall, new rainwater pushes the existing pipe water into the collection tank.

The benefit of this system is that it offers more flexibility since the collection tank can be anywhere on your property. Also, it can look cleaner since the pipes are underground.

One drawback of the wet system is that it is more expensive than a dry system (ditch digging is necessary). Another is that it requires more upkeep to ensure water quality since there is stagnant water in the pipes. Pipes with stagnant water can become a breeding ground for insects and lead to anaerobic fermentation if lines aren’t drained from time to time.

One approach isn’t better than another. The system you choose depends on the layout of your property, aesthetic preferences, preferred levels of maintenance, and budget.

the Rainwater Management Solutions 4-Step Wisy System 

Using the RMS Wisy 4-step system gives you the best water quality possible while dramatically reducing the time and effort needed for system maintenance. The RMS’ low-maintenance approach to rainwater harvesting is a prime example of the age-old adage to “work smarter, not harder.” Here are the steps.


Although rainwater is very clean, often the collection surface is not. As it flows down the surface, water can pick up debris and contaminants that can be harmful if left sitting in the storage tank. For this reason, filtering the water BEFORE it enters the tank is paramount. Prefiltering removes large particulates from the water, resulting in much cleaner tank water, benefiting both users and equipment alike.


With incoming water free from large debris, a device called a ‘Smoothing Inlet’ now has work to do. Its job is to oxidize the water and introduce it into the tank gently enough not to disturb any beneficial bacteria-eating biofilm on the bottom of the tank. It does this by directing water in an upward and outward flow near the surface level. Once accomplished, the water is now safely contained and ready for consumption at a point in the future.  

step three: floating filters

The tank water is also removed with great care when ready for use. Tiny sediment particles typically settle to the bottom or float on the water’s surface. For this reason, a device called a floating filter draws water from the middle where it’s at its cleanest.

The floating filter consists of a ball-float with a filter attached underneath, connected to a food-grade suction hose. As water enters the filter, it passes through an outer and inner filter. The outside filter strains sediment greater than 1.2 mm, while the inside removes particles larger than 0.3 mm. This method ensures that water is cleanest for humans and the machines that pump it out.

step four: overflow

The final step in the WISY process is to set up an overflow system. If you let too much water into the tank, it will go back up the inlet pipe or create unwanted pressure on the tank. An adequately installed overflow system allows for easy removal of excess water. This process also removes any tiny particles from the surface water.

Choosing an overflow device with a mechanism designed to protect against small animals from entering the tank is wise. Also, find one with a ball-float backwater valve to prevent any potential stormwater backup from entering the rainwater collection tank, like this overflow protection device.

Final Thoughts

People have always needed to collect and store water. Whether using that water to grow crops, cook with, provide drinking water for themselves or animals, or modern-day uses in a grey water system, such as vehicle cleaning or flushing toilets.

There are many different methods to collect rain and stormwater and many aspects to consider, such as your tank size and treatment methods.

Suppose you are interested in being a water steward on a small or large scale. In that case, there is a wealth of information, and many people eager to help you succeed. In fact, RMS’ founder David Crawford started as an enthusiast and made rainwater harvesting his full-time profession. 

If you are looking for water tanks for sale, pumps, filtration systems, or any other component of a rainwater collection system, check out what RMS offers here.

If you have any questions about rainwater collection for a specific project or questions about any other products we sell, please contact us.

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