Rain Barrel Overflow Solutions

This article explores methods of diverting the overflow from a BlueBarrel Rainwater Catchment System™. Our downspout diverter automatically directs rain barrel overflow down through the existing downspout without any effort, but there’s so much more you can do with that valuable resource of excess water. Read on for multiple sustainable rain barrel overflow solutions, to transport, infiltrate, and store that precious rainwater!

You've Got Your Rain Barrels - Now What?

So you’ve installed a BlueBarrel System and you're all set to collect the rainwater that cascades off your roof. Collecting rainwater in barrels or tanks is referred to as active rainwater harvesting. You’ll see the water level in your barrels going up and down as you use water from the system and fresh rain fills it back up.

But what happens with excess water when your barrels are full? Rain barrel overflow gives you an opportunity for passive rainwater harvesting. Passive rainwater harvesting simply means collecting rainwater in the ground, allowing it to infiltrate. You can do this with a variety of techniques that I'll delve into in this article. 

Both passive and active rainwater harvesting are excellent for the environment. The main difference is active rainwater harvesting allows you to store water for irrigation and other uses. Passive rainwater harvesting simply directs water back into the ground to hydrate soils and recharge groundwater, as it would do in nature.

You may realize you could add more barrels to your setup. Even after doing your roof calculations it is hard to believe just how much water accumulates in a brief rain shower! But even so you will have overflow, so let's look at the best ways to deal with it:

rain garden example
This planted, rock-lined swale is a great example of passive rainwater harvesting in the landscape.   Photo courtesy of the Kitsap Conservation District.

Designed for Overflow

Even in arid regions, your barrels will reach their capacity and overflow. You get over 600 gallons of high-quality irrigation water for every single inch of rain falling on a 1,000 square-foot rooftop. Just to give you an idea, that’s enough to fill 11 standard 55-gallon barrels... for every single inch of rainfall!

Our overflow-handling downspout diverter is one of the most brilliant parts of the BlueBarrel Rainwater Catchment System design. It shifts the flow of water from the barrels and directs it back down the existing downspout automatically when the barrels are full. In other words, any time your rain barrels are full, rainwater will flow out as it did before you had a BlueBarrel System. 


Downspout Diverter system overflow
A BlueBarrel downspout diverter.

How Downspouts Work

Before we talk about utilizing this precious overflow of rainwater, it helps to understand how your downspouts work in the first place. This is because the BlueBarrel System allows your downspouts to function as normal after barrels fill.

Note and Caution: BlueBarrel is very unique with our built-in overflow solution! Many systems require you to cut your downspout. This also requires you to invent a safe and effective overflow solution. Otherwise, you will be left with uncontrolled runoff at the base of the rain barrel, which can jeopardize nearby building foundations.

Remember, your home probably has multiple downspouts (one or more for each stretch of roofline). Each one may utilize a different method for directing overflow away from the foundation. Some common methods include:

system overflow downspout drop off into grass
downspout plastic tray
downspout connected to pipe
Downspout drop-off: Your downspout just ends where it meets the ground (perhaps with an elbow and short extension). The water is left to pool and infiltrate in situ. Ideally, the ground slopes away from a building, but it’s never a good idea to create a wet-zone near a building's foundation.
Splash block or flexible drainpipe: A 2’ tray or a segment of flexible plastic pipe carrying water that much further from the end of the downspout. These often empty onto a lawn or other planted area. A slightly better method than the drop-off, these direct water further from the foundation, preferably towards a permeable surface where it can infiltrate.
Built-in drainage system: The downspout connects to underground drainage pipe, carrying overflow to the street or into your household wastewater system. This method keeps water away from your foundation, but carries this precious resource all the way to the municipal water works where it will be treated with wastewater and sewage. This vital infrastructure is often overwhelmed during rainstorms, leading to issues with runoff control and combined sewer overflow.

Rain Barrel Overflow: Slow it, Spread it, Sink it

Slow it, Spread it, Sink it (and Store it!) is a popular mantra amongst water stewards. This is a sustainable contrast to the modern water systems’ standard: Pump it, Pipe it, Pollute it. 

Ideally, you want to direct rainwater away from buildings while keeping it on your property as long as possible (slowing the flow). This encourages water to spread across the landscape and infiltrate (sink!) into the ground.

Why is infiltration important? Infiltration is the vital link in our global hydrologic cycle that hydrates plants and soils, and recharges groundwater underfoot. 

The planted, natural, permeable surfaces surrounding your home are likely able to accommodate the average rainfall. Soil acts as a sponge, and plants soak up water through their roots. However, the non-permeable surfaces on your property—including roofs and pavement—prevent infiltration. They shed water and create unnatural amounts of runoff. If your property has a high ratio of impermeable (roof, driveway, patio) to permeable surfaces (gardens, gravel) you will want to direct the course of runoff into the permeable areas in an effort to slow it, spread it, and sink it into the ground.

You can increase permeability on your site by tearing up hardscape where you are able. Dig basins and swales (which can be beautiful!), to give water a place to sink into the ground. See the infiltration basin diagram below for further details on their ecological benefits.

When you slow the flow of water it is more able to permeate the land and percolate through layers of earth. A fast-moving stream will continue flowing downhill (think: gutters, street curbs, rivers), but if you can intercept this stream in a flat wide basin in order to spread the water out across a larger, permeable surface area, it will then be able to sink back into the ground.

infiltration basin example diagram

A Better Place for Overflow to Go

Your rainwater catchment system is a great way of intercepting roof run-off and distributing it throughout the green spaces around your home. But your garden (and Mother Earth) will get maximum benefit if you direct the overflow to permeable ground that can infiltrate excess water. This way, you combine active and passive rainwater harvesting techniques. Below are some options for managing and utilizing rain barrel overflow.

Taking cues from a Riverbed

We have seen many creative overflow handling systems form BlueBarrel's own customers. Bill, of Pelham, NY, lined an infiltration channel with gravel and river rock. The channel carries his rain barrel overflow away from his house and downhill towards a larger gravel-filled depression. The larger basin serves to infiltrate just about all of the water coming from this downspout. 

rain barrel overflow catcment drainage
A passive inflitration set-up form a BlueBarrel customer in Pelham, NY.

Remember, because BlueBarrel's downspout diverter handles overflow automatically, Bill's two rain barrels will fill first. When they are full, excess water course down his downspout, through the drainpipe, and into the rocky channel.

Rocks and gravel are especially useful for slowing the flow of water and are an attractive alternative to perforated pipes. As an added bonus, Bill's adjacent flower beds will benefit from the rainwater percolating into the ground near the roots.

Rain Gardens

This method uses plants to uptake and infiltrate overflow and runoff. Let’s say you were to use Bill’s method, above, to channel overflow downhill and away from the house. In this version, however, the water is directed into a shallow basin filled with specially selected plants. An ideal rain garden plant palette includes species that tolerate wet feet (after a rainstorm when the basin fills with water) and can also withstand dry periods (between rains when the basin dries out). Rain gardens usually have their own overflow system (because sometimes when it rains, it pours!). This may be an outlet that directs overflow further downhill and/or an elevated overflow drain that is piped away from the rain garden. 

Expert tip: Rain gardens and infiltration bases should sit at least 15' away from building foundations. Ask your local Master Gardeners for a regionally-appropriate rain garden plant list!

Rainwater Storage 

If you live in a dry climate or are particularly attuned to the benefits of rainwater for your plants, you may be wondering: why can’t I hold onto that precious rainwater? Well, you certainly can. Our Add-On Kit allows you to easily add more barrels to your existing BlueBarrel System, increasing your holding capacity. But what if you’re maxed out and you just don’t have room for more barrels near your downspouts? Or what if you simply want to store some water in a more convenient location (e.g. closer to your garden, rather than right next to the house)? 

You might consider building a non-roof-tied BlueBarrel System in a more convenient location (contact us to special order your kit without a downspout diverter). You can then pump water from one system to another to free up capacity in the barrels that fill fastest, increasing your capacity for stored rainwater. 

A beautiful Monterey Bay rain garden example  from green-gardener.org.
Add on additional barrels to your existing BlueBarrel System for extra rainwater storing capacity.


But I must end by affirming, no matter how much storage capacity you install, expect overflow. The earth is our biggest water tank, and allowing rainwater to infiltrate into the ground to hydrate soils, activate the rich microbiology that lives there, and recharge groundwater is the absolute best way we can steward water onsite.


Article by Olivia Loughrey, BlueBarrel staff writer, MS ecological design.


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