Well, this simple answer to this question, is: it depends on what you are trying to accomplish with rain barrels.
I Want to Store Water From My Roof to Use For Irrigation
Rain barrels work well to collect rainwater that is coming off your roof and save that water for later use in irrigation. Simply purchase a barrel, which is just a water storage container, install it adjacent to one of your downspouts and divert that downspout into the barrel, and there you have it: water storage that can be used for the garden.
Life Is Never This Simple Though, Is it?
In my experience, most rain barrels are simply full of water and draining next to the foundation. If you do not install an overflow drain at the top of a rain barrel, it will not provide adequate control of roof runoff and it could allow roof runoff to drain next to the foundation. Thousands of gallons of water can come off your roof during heavy rains. That barrel can fill up quickly. During heavy rains, overflowing rain barrels can lead to basement, crawl space, or slab moisture control problems and it can even lead to structural settlement over time. This is because water washes away the fine particulate in soils and the soils no longer bear weight well. Think of when you are at the beach and the water from a wave rushes over your feet and then back out to sea. What happens? You drop down in the sand right? The same thing can happen with your foundation.
So You are Saying I Need an Overflow Drain for My Rain Barrell?
Yes. But you also need a place for that drain to run into! An overflow drain that drains next to the house is not going to help with moisture control around the building – see the photo above. So, you also need to install or have some type of storm drain into which to run the overflow water in your barrel – see the photo below. In this picture, the water can fill up the barrel and when the barrel is full it has a place to run into – the storm drain. But what is one problem you see with this installation?
An Overflow Needs to Be Properly Sized
The drain hose or tube for the picture above is too small and will not be able to keep up with the inflow during heavy rains. This could lead to an overflowing rain barrel. Rain barrels should also have a way of filtering the water so they do not become obstructed with leaves, needles, and sticks. And they also need a place to connect a hose so the water can be used later.
Rain barrels can be a great way to store roof runoff water for irrigation, but they are more complex to install than simply diverting your downspout into a barrel. A well-designed system can save water AND control roof runoff, while a poorly designed system could lead to costly moisture control problems.
I hope this article helps. For more tips on looking at houses, see The Confident House Hunter.