Downspout Connections for your Rainwater Harvesting System!


As we get ready for the autumn rains, it’s time to connect our rainbarrels to the downspout and enjoy the sky’s liquid bounty! Read on for tips and hints about downspout tie-ins from BlueBarrel!

BlueBarrel Rainwater Harvesting Systems

Blue Barrel Systems Facebook
Blue Barrel Twitter
Blue Barrel

Overflow Outlet

Notes on Overflow

Unless you choose a downspout diverter that manages overflow automatically (see prefab options in the body text), you will need to drill a second hole in your system to serve as an overflow outlet. You can direct overflow to a raingarden (preferred by Mother Nature and our senses!), or to an existing storm drain.

To install an overflow: Simply drill a hole at the highest possible point on the side of any one of the barrels in your BlueBarrel System. Use an insert ell to transition from your newly drilled hole to your overflow pipe or hose. As always, you will need to cover the overflow opening with 1/16” mesh to prevent critters from making their way into your tanks–you can just pinch some into place along with your insert fitting. Seal any gaps in the opening with silicone if necessary.

Sizing Details: Best practice (and forthcoming CA plumbing code addressing rainwater catchment) dictate that your overflow outlet must be at least as large as the sum of all inlets. This is to make sure that you don’t have water entering your tanks at a faster rate than it can exit, which would cause backup in the inlet pipe and possible leakage or damage to your conveyance system.

In the example to the right, because I used 3” flex drain, I should technically have a 3” overflow, but a hole that large in the side of my barrel would decrease my storage capacity more than I would like. Instead, I drilled a 1.25″ overflow. I haven’t had a problem because my catchment surface is small enough that local rainfall rates aren’t likely to overwhelm a 1.25″ outlet, but if I had it to do over again, I would use smaller inlet pipe to satisfy this best practice. An added benefit to having inlet pipe size match overflow pipe size is that you can use the same hole-saw bit for drilling both ports!

Disconnected Downspout Tie-In

Keepin’ it Clean!

Since your first flush of water will be quite dirty with the summer’s accumulation of leaves and debris, you may wish to wait for the first rain to pass before connecting your system. You can get your tie-in all hooked up ahead of time, and simply leave it disconnected (as in the photo above) until that first rain passes. This will also allow you to observe how water flows through your downspout connection before you commit it to your collection vessel. Be sure to protect any disconnected openings that lead to your barrels with 1/16th” mesh (a rubber band is a great way to secure mesh in most cases).

You will want to clean out your gutters before the rains begin–lest you make and store ‘rainwater tea’ with nature’s deposits! It is recommended to clean gutters each season if you have a rainwater collection system, but if you don’t quite get to it that often, just know that now (end of summer, before the first autumn rain) is the most important time to clean any gutters that lead into a rainwater catchment system.


First Flush Pipe

First Flush Diverters

Speaking of keepin’ it clean, a first-flush diverter is an optional component that you can install upstream of your storage vessels to catch the first quantity of water (usually the dirtiest) in a storm event. The concept is simply a pre-chamber (in this case a capped segment of 4″ PVC pipe) that receives the first few gallons of rain along with the heaviest load of particulates. As the first-flush pipe fills, most sediments will settle to the bottom, and cleaner water will spill over into your tanks. The cap must be removed periodically to release debris.

Consensus is lacking amongst rainwater harvesting professionals about the virtue of first flush systems, as there is no way to determine exactly how many particulates are diverted from your system, and 1/16th” pre-filtration is necessary regardless. Most recognize first-flush devices as an optional second line of defense that is likely to improve your stored water quality if maintained correctly. Please note that a first-flush diverter is not a replacement for the required 1/16th” pre-filter, which still must be installed upstream of your first-flush if you choose to install one.

Demystifying the Downspout Connection

By Jesse Froehlich Savou, ARCSA A.P.

September, 2012


Since this blog post was written, BlueBarrel has evolved to provide easy do-it-yourself (DIY) kits, including a user-friendly downspout diverter that will insert into your existing downspout and handles overflow automatically. We stock round and rectangular versions! The downspout diverter comes standard with our DIY RainKit, and we also offer it as a standalone in our online store

Hello !

I hope the new season finds you well! Now that autumn has arrived, we’re just waiting for the sky to open with a fresh flush of rain. It’s time to get those gutters cleaned out and to complete that downspout connection in order to be ready to catch as much free-falling rain as you can store!

Often, the last part to complete with a rainwater harvesting system is the downspout connection. I always remind folks that every downspout tie-in is a custom downspout tie-in and you have many options. Because the BlueBarrel System is designed to allow multiple barrels to function efficiently as one larger tank, you will only need to install one inlet to serve all of the barrels in your system. By contrast, if you have multiple free-standing barrels or cisterns, you will need a downspout connection for each. If you’re still looking for the right solution for your own system(s), read below for my notes on a handful of approaches.

Simple Home-Made Downspout Connection

I used a a very quick and inexpensive (yet highly functional) method for my first downspout tie-in: I simply removed the existing downspout and routed all water through my BlueBarrel System using inexpensive Flex-Drain.

Simple Downspout Connection

I drilled an entry port for the pipe on the top of the closest barrel using a hole saw, and used some silicone caulking to seal the opening after inserting the Flex-Drain.

A 1/16th” rough filter on the inlet is required for keeping leaves and insects out of rainwater catchment systems. To meet this requirement, I simply taped some 1/16th” fiberglass screen to the pipe entry (leopard print duct tape optional!). You can purchase a roll of fiberglass mesh at the hardware store, or re-purpose an old door or window screen.

Finally, I used a pipe strap against the wall to hold the Flex-Drain in place.

Voila! One hour and ten dollars later, my original BlueBarrel System was ready for the rain!

If you choose this simple and inexpensive method for your downspout connection, you will need to drill a second hole in your system to serve as an overflow. Luckily, crafting an overflow is just as easy as crafting an inlet. See the sidebar for some detail on how to install an overflow.

Prefab Downspout Options

As rainwater harvesting gains popularity amongst environmentally- and resource-conscious gardeners, many prefab options for pre-filters, downspout diverters, and other accessories are hitting the market. Every time I go the hardware store I find new products on the shelf. Friedman’s Home Improvement, with locations in Sonoma and Mendocino counties, has been my most consistent source for rainwater harvesting accessories. Harmony Farm Supply in Sebastopol is a tremendous resource for irrigation supplies and expertise, and will be stocking their shelves shortly with various options for rainwater harvesting. The Urban Farmer Store is another trusted source for rainwater harvesting equipment for those in Marin, San Francisco, and the East Bay.

There are many options out there. Read below for my notes on installing just a few of them.

Leaf Eater Advanced

‘Leaf Eater Advanced’ rain head
by Rain Harvesting

This option is an easy upgrade to the simple downspout connection described above. The Leaf Eater simply replaces the duct-taped fiberglass mesh that I had used originally. It serves to keep leaves, insects, and large particulates out of my BlueBarrel System. Installed at a level that I can reach without a ladder, I simply remove the slanted steel mesh plate and rinse away debris any time there seems to be an accumulation.

Because of the placement of my downspout, I installed a downspout elbow to direct flow through the filter.

Note: This product is for pre-filtration only, and does not include an automatic diverter. It can be installed upstream of any diverter product you may choose. Besides the Leaf Eater, the conveyance system depicted here is the same as the home-made connection described above.

'Rescue' Downspout Diverter & Connector Kit

downspout diverter kit
by Emsco Group

My newest 6-Barrel system collects water from a downspout on the front of the house. For this highly visible connection, I wanted to try one of the smaller and more visually streamlined options. This simple diverter requires cutting the downspout using a hack-saw–probably the most intimidating part of installing a diverter! Water collects in the upper chamber of the diverter and spills through the 1/2” hose, which must be installed level to the highest fill-level of the barrels. Beause the hose is only 1/2″ in diameter, in heavy rainstorms excess volume will spill over through the downspout’s original route. Likewise, when my BlueBarrel System is full, new rains will back up through the hose to the diverter, again overflowing down the original downspout. Because this piece handles overflow automatically, there is no need to install a separate overflow outlet.

Note: Because this diverter does not include 1/16” filter protection, I needed to take care of this separately. One option would be to install a Leaf Eater similar to the product depicted above, upstream from the diverter. Instead, I simply pinched a small piece of fiberglass mesh in as I inserted the hose into the diverter. I will need to remove and flush or replace the mesh periodically.

'Clean Rain' Downspout Diverter

‘Clean Rain Advanced’ downspout diverter
by Rain Harvesting

Another product by Rain Harvesting, this diverter actually includes the standalone Leaf Eater from the example to the left as a built-in component. Notice that because of the particulars of my downspout in relation to the wall, I did not need a gutter elbow in this case. In theory, this product automatically senses the dirtiness of the water and directs the “first-flush” down it’s main barrel away from my BlueBarrel System. Once this first flush of dirty water has passed, an internal valve is triggered and clean water spills through the green hoses into my barrels. (See sidebar for how to build your own first flush diverter.)

There is also a manual switch that allows me to control the destination of the water. This piece comes equipped with two outlet ports, allowing the option to serve two different systems. I wanted all of my water to go to my BlueBarrel System, so I directed both hoses to the same place. I could have drilled a small hole in the top of the barrel for each hose, but instead I drilled one larger hole, and inserted a re-purposed garden pot (lined with 1/16” mesh, of course!) to catch water from both hoses. I’m curious to see how well this product works!

Note: If you look closely, you can tell that this picture was taken in the same location as the larger photo above. I replaced the original Flex-Drain connection with this hi-tech alternative. Until it rains I won’t truly know which method works better, but let this be a demonstration of how easy it is to modify and upgrade your BlueBarrel System as you have the time, inclination, and budget!

BlueBarrel Rainwater Catchment Systems

More about BlueBarrel!

I hope you have found these tips on downspout connections to be helpful! Please share this mailing with others you know who are interested in rainwater harvesting as a water conservation technique.

BlueBarrel is committed to bringing people into alignment with the environment’s capacity to support and sustain us, for a greater sense of self-sufficiency and shared abundance in natural resources. We provide custom design, installation, and consultation services to homeowners, schools, and business owners interested in harvesting rainwater on-site for irrigation needs. We also offer periodic workshops and DIY kits! If you would like to consider a BlueBarrel System as your rainwater harvesting solution, contact us at Our website is under construction, but in the meantime you can to stay updated.

Click the ‘Like’ button below to share a link to this newsletter on your own Facebook page!

Copyright © 2012