A 9-Step Guide To Building A Rainwater Collection System

Have you ever considered your high water bills and wished for a solution? With increasing concerns about water scarcity and the urgent need for conservation, it's time to explore sustainable practices.

One of these is a rainwater collection system, a simple yet effective method to curb water usage and potentially lower those pesky utility bills. You can save so much water and use it later for other purposes, such as for watering weed seeds outdoor.

Besides, being self-sufficient and having an emergency water supply when living off-grid or in drought or disaster-stricken areas can be life-changing. This comprehensive guide will help you build your rainwater collection system. Dive in!

Understanding The Basics Of Rainwater Harvesting

First things first, understand what rainwater harvesting is. Simply put, it's the practice of collecting, storing, and utilizing rainwater for later use. From watering your garden, flushing your toilets, to even drinking (with proper filtration), this system can drastically reduce your reliance on municipal water. 

Besides lowering utility costs, it's a significant step towards water conservation, potentially saving thousands of gallons of water annually. In areas with frequent water shortages or high water costs, rainwater harvesting isn't just a practical solution; it's a game-changer.

Legal Considerations

Before you start setting up your rainwater collection system, it's crucial to understand the legalities. Yes, you heard it right! There may be local laws and regulations around rainwater collection. These laws vary widely, with some areas fully supporting and encouraging these practices, while others may have certain restrictions.

These laws dictate who can use water from natural sources, like rain. The idea is that if someone collects rainwater, they reduce the amount that would naturally flow into rivers or underground reserves. This could affect other people or wildlife that rely on these water sources. So, while it might seem strange, these laws are meant to protect everyone's access to water. 

It's always best to check with your local municipality or county office to ensure you're not crossing any legal lines.

Site Assessment

Choosing a suitable location for your rainwater collection system is more critical than you might think. A site assessment for a rainwater collection system might seem simple, but there's more to it than meets the eye. Your roof's size and material are important. A more extensive roof means more area to collect rain, and certain materials like metal are better at capturing and channeling water than, say, wood shingles. Also, your roof must be clean and free from contaminants since dirty water is less valuable and could harm plants or people if misused.

But don't forget about local rainfall rates. You might have a large metal roof, but you won't collect much water if you live in a desert. You'll also need to consider the quality of the rain in your area. Is it often mixed with dust or pollution? If so, you might need a more robust filtration system.

Last but not least, consider what's around your home. Are you next to a factory that emits smoke or a tree that drops leaves onto your roof? These factors can contaminate your rainwater and complicate your collection process.

So, choosing the right site isn't as simple as it looks. But with careful thought and planning, you can maximize your system's effectiveness.

Calculating Rainwater Yield

Now that you have your site, it's time to talk numbers. Calculating your potential rainwater yield is essential to understanding how much water you can realistically collect. Your roof size and local rainfall data are critical to this calculation. 

Here's a simple formula: for every inch of rain that falls on a 1,000-square-foot roof, you can expect to collect about 600 gallons of water. So, if you live in an area where the annual rainfall is 30 inches, you can potentially harvest 18,000 gallons of water in a year! Imagine the possibilities.

open rainwater system

Designing The Rainwater Collection System

A typical rainwater collection setup includes three main components: the catchment area (your roof), the conveyance system (gutters and downspouts), and storage (tanks or barrels). 

Your roof is the catchment area where rainwater is collected.

The perfect roof for rainwater catchment has a few key traits. First, it's large.

More surface area means more rainwater collected. Second, it's made of a suitable material. Metal, slate, or tile roofs are great as they're smooth and don't absorb water. Third, it's clean and free from debris or contaminants. You wouldn't want dirt, leaves, or bird droppings in your water. Finally, it should be angled to guide water into your collection system.

Eavestroughs and siding are also integral to a rainwater collection system. The eavestrough channels rainwater from the roof to the downspout, while the siding protects your home from water damage. When designing, ensure your eavestrough is large enough to handle peak rainfall and slopes slightly towards the downspout. Choose durable, non-toxic materials for both eavestrough and siding, considering your climate and the intended use of collected water. A reliable eavestrough & siding company will help you choose the best materials and install the components correctly.

The conveyance system comprises gutters and downspouts, which channel the water from your roof to your storage tank. When designing and installing these components, there are several essential considerations. First, choose durable, rust-resistant materials. Aluminum, stainless steel, or PVC are excellent choices. 

Second, ensure the gutters have the correct slope for water flow, usually 1/2 inch for every 10 feet. Third, the downspouts should be large enough to handle peak rainfall. Fourth, use gutter guards to keep out debris like leaves or twigs. Finally, the downspouts should direct water into your storage tank, and an overflow outlet is essential for handling excess rainwater. 

Selecting And Installing A Storage Tank

Choosing the right storage tank is crucial to the success of your rainwater collection system. When selecting a tank, consider its size, material, and location. 

When choosing a tank for your rainwater collection system, consider your water usage, rainfall frequency, and roof size. First, estimate your water needs. Will the collected water be for gardening, flushing toilets, or drinking? This determines your required tank size. Second, consider local rainfall patterns. Areas with regular rain might need smaller tanks, while drier areas may need larger ones for storing water between rains.

Third, remember your roof size. An enormous roof will collect more water, necessitating a bigger tank. Lastly, consider the available space for the tank and the budget. These factors together will help you find the right tank size.

Material-wise, durability is critical - materials like polyethylene and fiberglass are tough and long-lasting. Second, consider the tank's light-blocking ability. Tanks that block light prevent algae growth, keeping your water cleaner. Third, the material should be food-grade if you plan to use the water for drinking. Finally, consider cost and availability in your area. 

For the location, opt for a spot close to your downspouts and usage points to limit the need for long pipes. The tank should also be in an accessible area for maintenance and cleaning. If it's large, ensure the ground is sturdy enough to support the weight when full. Moreover, consider the tank's visibility, depending on your aesthetic preferences. Lastly, a higher location is preferable if you're using gravity for water distribution. Proper location will ensure your system runs smoothly.

raing water collecting

Implementing A Filtration And Purification System

So, you've collected your rainwater, but before using it, especially for drinking, you must filter and purify it. This process removes debris and potentially harmful bacteria. 

Basic filtration systems can be as simple as a mesh screen on top of your storage tank. The mesh screen acts as a pre-filter, catching larger debris like leaves, twigs, and insects. The screen should be sturdy, rust-resistant, and easy to clean, with a mesh size small enough to trap debris but large enough to allow water to flow.

For installation, it's vital to secure the mesh screen tightly to prevent debris from entering the tank. Regular cleaning of the mesh screen is also crucial to ensure unimpeded water flow and maintain the quality of the collected rainwater.

However, more advanced purification methods are needed for drinking purposes, such as UV light or reverse osmosis systems. Designing a UV filtration system for rainwater involves a few steps. First, you'll need to position the UV filter after any other filtration systems to ensure the water is clear of particles. This improves UV light penetration, making the system more effective. When installing, ensure the system is easily accessible for bulb changes and maintenance. Remember that UV filters require electricity, so plan for a power source. Proper setup will guarantee safe, clean water.

Reverse osmosis (RO) filtration is a process that removes contaminants from water by applying pressure to force water molecules through a semipermeable membrane. In a rainwater collection system, you'd position the RO system after preliminary filters to protect the membrane from large particles. For installation, follow the manufacturer's guidelines closely. Remember, RO systems produce wastewater and require regular filter changes. So, planning for these aspects is critical to a successful setup.

Keep in mind, though, these advanced systems may increase the overall cost of your setup.

Maintenance And Troubleshooting

Your rainwater collection system is not a set-it-and-forget-it solution. Regular maintenance is vital to keeping your system healthy and functional. This includes routinely cleaning your gutters, checking your tank for leaks, and maintaining your filtration system. 

But what if you encounter issues? For instance, low yield could be due to blockages in your conveyance system or inadequate roof size. Always inspect your setup for potential problems and troubleshoot accordingly. With regular checks and prompt issue handling, your system will serve you well.

Cost-Benefit Analysis

Setting up a rainwater collection system has initial costs, including purchasing a tank, installing gutters and downspouts, and implementing a filtration system. Depending on your chosen design and materials, these costs can vary. However, the long-term benefits can far outweigh these initial costs. 

For one, your water bills can significantly drop, potentially saving you hundreds, if not thousands, annually. Additionally, the environmental benefits are priceless. You're not only conserving a precious resource but reducing your carbon footprint, too, by lessening the demand for treated municipal water.


Water is essential for life, and its conservation has never been more critical. As discussed above, a rainwater collection system can effectively tackle water scarcity and high utility costs. 

But remember, it's crucial to consider your own needs, local climate, and regulations before you start. If you're unsure, don't hesitate to seek professional advice. Ultimately, adopting rainwater harvesting is not just about personal benefits, but it's a step towards a sustainable future. 

So, why wait? Start planning your rainwater collection system today! Remember, every drop counts.

Author - Olivia Poglianich
Olivia Poglianich          

Content Strategist

Olivia Poglianich is a nomadic brand strategist and copywriter in the wooden crafts and 3D product design space who has worked with brands such as Visa, Disney and Grey Goose. Her writing has taken her all over the world, from a Serbian music festival to a Malaysian art and culture event. Olivia is a graduate of Cornell University and is often writing or reading about travel, hospitality, the start-up ecosystem or career coaching. Her latest interests are at the intersection of web3 and communal living, both on and offline.



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