Recent drought and water use restrictions have highlighted the need for more water capture systems. Also, known as rainwater harvesting, these systems collect runoff water from your gutters and store it for future use. This post is about how I built my rainwater harvesting system.
What is Rainwater Harvesting System?
In rainwater harvesting, stormwater runoff is collected in containers for future use. Some common uses can be for irrigation, gardening, washing, and water features. Without proper filtering, rainwater harvesting is non-potable or not drinkable.
energy.gov
The Best Containers to Store Rainwater
Using the proper container for your Rainwater Harvesting System is important. There are many different container options and it’s important to determine what the harvested water will be used for in order to get the correct container.
The best containers are made of dark-color, food-grade plastic, with a sealed lid. The most popular choice of container is a 55-gal Blue Drum. This FDA-approved shipping container has a tight head with two 2-inch openings. Here are the ones I used for my Rain Harvesting System.
55-gal Blue Drums are a very common food-grade shipping container. They are generally only used once to prevent cross-contamination. Previously-used drums are available for purchase in most areas. I bought mine off Craigslist. A quick search online should find 55-gal Blue Drums in your area OR you can [click] on the link below to have the search done for you.
Let Me Google That For You https://letmegooglethat.com/?q=previously+used+55+gal+Blue+Drum+near+me [click on the link above to view search results in a separate window]
I decided to use (2) 55-gal Blue Drums as storage in my rainwater harvesting system.
How to get Rainwater into a Container
Most buildings have gutter systems to channel water from your roof down to the ground. These gutter systems are generally made of PVC or aluminum. Galvanized metal gutters should not be used to collect rainwater because hazardous chemicals can be present in aging galvanized pipes.
To get the rainwater from the gutter into a drum you’ll need a downspout diverter. This device requires you to cut your downspout and fit it in between the 2 ends. A standard downspout is 2×3 or 3×4. It’s important to measure the height of the 55-gal Blue Drum to insure the diverter is positioned above.
Downspout diverter 
Diverter slips over downspout 
Diverter acts like a sleeve
A rain barrel needs regular mainenance, particularly:
Chesapeake Bay Foundation
• Draining water before every storm
• Removing leaves and debris
It is important to avoid debris getting into the barrel. Decomposing leaves will grow bacteria in the water and make it unusable. One way to avoid leaves is to put a debris filter at the top of your downspout.
Debris Screen Placement 
Downspout Debris Screen 
Looking down a Debris Screen
Positioning Rainwater Storage Container
Getting the water into the drum is only half the battle because you need a convenient way to use that water. The water from a rainwater harvesting system is gravity fed and won’t have the same pressure as water a domestic plumbing system. This is because the weight and height of the water storage, in a rainwater harvesting system, are what determine the water pressure. This is why you usually see tall water towers around town or on top of buildings. Most rainwater harvesting systems are put on stands to elevate them and get better water pressure.
A 55-gal Blue Drum filled with water weighs about 450 lbs. It’s important to accommodate the full weight in order to correctly size a support stand. I chose to build my own stand to support (2) 55-gal Blue Drum.
PT Lumber Sized and Cut 
Detail of spreader Tusk Tenon 
Detail of Mortis Tenon 
Assembly of all the pieces 
Tenons tapped through mortise joints 
Staining and Sealing Wood 
Pipe Strap Drum Support 
Finished Stand
I built this stand to support the 55-gal Blue Drums on their side so the bung holes would be best aligned for plumbing the rainwater harvesting system. I’ve made my shop drawings for this stand available on ETSY for download. If interested click on the link below.
Plumbing Rainwater Harvesting System
Once everything is in position, it’s time to connect everything together. 55-gal Blue Drums come with (2) Bung holes. The caps usually have a 3/4 inch knock-outs in them. The threads on the center knock-outs are National Pipe Taper (NPT).
Top and bottom caps 
Top cap with open center 
Bottom cap with center knocked out
I used a common garden hose to plumb the 55-gal Blue Drums together with 3/4 inch NPT to barbed adapters. The hose is held onto the barbs with 7/8 inch stainless steel hose clamps.
NTP barbed connector 
Plumbing to the diverter 
Connecting between the drums 
NPT to Hose Bib
Cost of a Rainwater Harvesting System
Most of the items I needed I purchased online at Amazon.com. Pricing is as of Sept 1st, 2022. Items pricing is beyond my control and subject to change.
Little things like pipe tape and hose clamps I picked up at my local hardware store. The pressure-treated lumber I picked up at the big box store. My total cost (not including labor) came in at roughly $500.
The most time-consuming thing was making the 55-gal Blue Drum stand. But you can get the plans for that on ETSY here: https://www.etsy.com/listing/1274037292/plans-double-rain-barrel-stand. All the measurements and materials are on the plans. I changed the tusk and tenon joints to pocket joints in the ETSY plans to make it a bit more simple for the DIY’er.
Practical Use of a Rainwater Harvesting System
My area in Central Massachusetts has been in Critical Drought conditions. I’ve had the Rainwater Harvesting System for a month and 2 passing thunderstorms filled both of the 55-gal Blue Drums. This has been more than enough water to keep a large vegetable garden green.
Thanks for Reading!
I hope this helps you get a Rainwater Harvesting System going at your house. If you found any of this helpful, please consider donating to the Blocks and Spots coffee fund. This keeps me motivated and helps me keep putting out these blogs.
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