DIY Files: Can I Stack Rain Barrels? Everything You Need to Know

Vertical Stacked Rain Barrels

This isn’t an approach we’d recommend. Do you know why? Read on!

It’s one of our most frequently asked questions: Can I stack rain barrels vertically?

The quick answer is yes. But there’s a but. A big one.

While the BlueBarrel Rainwater Catchment System in its classic form consists of one long line of barrels (you choose how many), some people have spatial constraints that lead them to seek space vertically. 

Barrels can be stacked to maximize space, but with each barrel weighing upwards of 500 lbs when full, it’s not feasible to support the weight of one barrel directly on another.

As a second point, if you wish to enjoy the advantages of an under-plumbed design like BlueBarrel’s, you’ll need space between each layer to allow for the plumbing, and proper ventilation.

To illustrate our recommendations for a successful stacked-barrel design, we’ll highlight an example, sent by customer Michael Nunn of Daytona Beach, Florida.

Thanks for sharing, Mike!


How to stack rain barrels

With Mike’s well-detailed diagrams, we were able to work with him to refine the plan and make sure he received all the necessary pieces in his custom-packed BlueBarrel DIY RainKit to build his custom design.

Vertical rain barrels

This diagram, provided by BlueBarrel customer, Michael Nunn, shows the key features of a safe and efficient vertical rain barrel setup.

Here are the key features of his design:

  • Each layer of barrels is supported by its own foundation. At 500 lbs per barrel (when full), a structurally sound foundation must be built to support the weight of each barrel.
  • Each layer has its own downspout connection. The specialty downspout diverter included with BlueBarrel’s DIY RainKits is designed to handle inflow as well as overflow. If installed with a level hose, as shown in Mike’s diagram, water will divert into the barrels until they are full. When barrels reach capacity, excess water will fall through an internal spillover to exit the downspout as normal. There’s no on/off switch for this – it happens automatically with this simple but brilliantly designed piece. In Mike’s case, the second diverter will catch most of this overflow to fill the bottom row of barrels. 
  • There is a shutoff valve between levels. Each barrel in a multi-barrel system must be vented so that air can escape as barrels fill with fresh water. If all barrels are connected via the underplumbing and served with one diverter at the top, water from upper levels will push out through the vents on the lower levels, keeping them from filling. Note the placement of the isolation valve. The valve will remain closed while barrels fill so that both levels can hold water. As Mike uses his water, the top barrels will drain first. Once the top set is empty, he can open the valve to access the water from the lower level. (Another possibility is to have a separate outlet on each level, so that no valve is necessary. In other words, build two separate BlueBarrel Systems, one on top of the other.)

Compliments to Mike for a job well done, and for sharing images with us as well. Here’s his finished project, now keeping his koi fish pond topped up with clean fresh water between Florida storms: 



Why not lay rain barrels on their sides?

stack rain barrels

What’s wrong with this picture?

Here is a design that is commonly found on the internet. Why not do it like this?

There are a number of reasons we recommend the underplumbed design instead:

  • With the bung openings offset a few inches from the edge of each barrel, laying drums on their sides leaves a substantial “belly” in the bottom of each barrel where water cannot be accessed. Multiply that loss by the number of barrels in your stack and that’s a lot of inaccessible water.
  • In addition to leaving water inaccessible, this belly will collect a sludge layer that can create turbidity in the barrels, leading to a heavy load of particulates in the water at the outlet. An underplumbed design flushes most sediments in real time, leading to naturally cleaner water. (Click here to learn why you want those little organic particulates to get to your garden rather than collecting in your barrels!)
  • With no ability to vent any barrels but the top one, and a narrow connection from barrel to barrel, it is unclear whether the bottom barrel will fill smoothly. A vent hole is necessary to allow air to escape as water enters, but unless carefully monitored and controlled, a vent hole in the bottom barrel would allow water to escape, preventing upper barrels from holding water.

Got a special situation, or need help customizing your BlueBarrel System? The knowledgeable team here at BlueBarrel is happy help you for a successful experience with rainwater harvesting. Give us a holler! We’re here to help. 


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