Learning Center

Find the answers to your home improvement questions.

How to Harvest Rainwater

Rainwater harvesting

Looking at your water bill month after month can be stressful. The cost might go up during the summer months when you’re using more water outside for your lawn or garden. Now there’s a solution where you can use a natural process to save water and cut down on your expenses. It’s called rainwater harvesting, and people all over the world have been doing it for thousands of years. There’s no reason to spend money on water every year when it can be collected for free.

When you harvest rainwater, the process is quite simple. When rain falls from the sky, it’s collected on the roof in a designated collection area. The water then moves down a transportation system that filters out any leaves or debris. Next, the water is collected in storage containers that are set up on the ground. This is the most important part, as they’re in charge of collecting all the water that comes down so it’s ready to use. The stored water can be used for cooking, drinking, and landscape irrigation. Let’s take a look at how to set up a basic rainwater collection system.

Setting Up the Collection Area

rainwater roof

The first step in starting the rainwater harvesting process is setting up the area where the water will be collected. This will be on the roof, as the water will eventually be going down a pipe and into a storage barrel. You’ll need to determine how much water you plan to collect before you set up the roof section. For a rough calculation, one inch will be collected per hour with moderate rainfall, based on the typical 25 foot by 40 foot roof. If you need to collect more water, you’ll need multiple downspouts with several barrels.

Installing the Transportation System

rainwater transportation system

Image via Flickr by Sustainable sanitation

Next, you’ll need to ensure you have a solid transportation system to get the water from the roof into the barrels. Based on how much water you determined you needed, set up the appropriate-sized gutters and downspouts. If you have a 5-inch gutter, you’ll need a downspout with a diameter of 3 inches. If your gutter is 6 inches, you’ll need a 4-inch downspout. They can be made from either plastic or aluminum — material doesn’t affect the rain harvesting. If your roof collect area is 1,000 square feet or smaller, these dimensions will collect more than enough rainwater.

Make sure you have a sturdy filter on the top of the downspout to protect your water from unwanted debris and bugs. Not having this can ruin the water if it’s to be used for drinking or bathing. Mosquitos and other bugs will be drawn to the standing water in the barrel, which is the last thing you want. Debris can also clog the downspouts, making them less effective. Aluminum, fine-mesh filters can be used to keep bugs and debris out. Double-check that they’re in the proper place, and do a test run while on the roof.

How to Set Up the Barrels

rainwater storage barrels

Image via Flickr by jbolles

All the hard work you just did now comes down to what’s storing the water — the storage barrels. If you’re using them to water your garden, place the barrels under the downspouts that are closest to the parts of your garden that need it the most. Make a base for the barrels by digging an area that’s 4 inches deep and the width and length of where you’ll place cinder blocks. To keep the blocks level and keep your foundation dry, put 1/4 inch of pea gravel in the area you just dug.

The higher the ground where you place your rain barrels, the higher the water pressure will be. It also makes it easier to put a spigot on the barrel, which you can use to fill a watering can. When full, these containers will be very heavy, so you want to make sure they’re easily accessible all year-round. If you need a good amount of water, you can attach short hoses to each barrel to connect them and increase the amount water you can store. If there’s a large amount of rain, overflow may occur from the barrels, but the 4-inch ditch will divert it away.

Advantages and Disadvantages


There are many advantages to installing your own rainwater harvesting system. It reduces water consumption and energy use more than water use from traditional indoor plumbing. This in turn saves money, as up to 50% of water consumption needed in most homes can use rainwater as an alternative. The barrels provide a backup system in case there’s a drought or the main system is damaged. It does require an initial investment to buy all the materials, and you need to make sure the system is set up correctly. Periodic maintenance is also required to make sure the filters still work and the tubes aren’t leaking.

The question of whether or not you should set up a rain harvesting system depends on how much water you’ll actually need. If you’re a typical single-family home just looking to save a little money on drinking water, it might not make too much of a difference by the time you’ve bought the materials and installed everything. However, if you intend to use it for all water purposes such as washing clothes, bathing, and watering your garden, this could be the right choice for you. You can set up multiple barrels and buy large ones to account for all the water you’ll need.

When looking to save money on your ever-increasing water bill, rainwater harvesting is definitely a great option. You don’t have to be a trained professional to install the system, and all the supplies are conveniently available at any hardware store. Once you get past the initial investment, the savings can be up to 50% off your regular water bill when using water from the storage containers.

Do you have questions about rainwater harvesting? Ask us in the comments section below!

(2) Comments

  1. BuildDirect Product Expert Team
    BuildDirect Product Expert Team - Reply

    Hi Panna,

    You can search “Rainwater Harvesting System” in Google along with your area and some local companies should come up. We are up in Canada so I’m not familiar with where you would be able to get one in your area. Please let us know if you have any other questions!

  2. I want to set up but need to know where to buy and what the system called and how much its cost and if any company can setted up for me. Thanks

Leave a Reply

Your email address will not be published. Required fields are marked *

You can use these HTML tags and attributes <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

Notify me of followup comments via e-mail. You can also subscribe without commenting.