Rain barrels can be great source of water for your lawn and garden. They can also cause a great deal of damage if they do not have a reliable water overflow. The water overflow in this design happens inside the downspout diverter. Once the rain barrel is full, additional rain water will overflow inside the downspout diverter and continue down the downspout. This system will fill rain barrels to a predictable level but not overflow the barrel. If you have ever needed to go out and check your rain barrel during a heavy rain storm because you were worried about it overflowing this design is for you.

Step 1: Filling the Rain Barrels

When the rain barrels are not full the water in the diverter’s reservoir drains down the hose. The water level in the hose equalizes with barrel because water seeks its own level.

Step 2: Full Rain Barrels

When the rain barrels are full the downspout diverter's reservoir overflows into the downspout. The water level in the barrel is at the same height as the top of the diverter's reservoir.

Step 3: Working Example

It looks odd to have the downspout diverter below the top of the rain barrel but this is critical to the design. I have used a collapsible section in the downspout to allow adjustment of the diverter height, this directly affects the max filling level in the barrel. It also seems little strange to fill the barrel using the small hole at the bottom but that is also critical to the design and works better that you may think.

Step 4: Downspout Diverter

You will need a downspout diverter that has a garden hose connection to provide a good seal when the barrels are full. Water needs to fill the reservoir in the diverter to the level that will overflow to the downspout below so you need a very good sealed connection to the barrel. Many downspout diverters use their own tubes and clamps that do not have good seals, they should not be used in this configuration.

I have also found that the connection between the diverter and the downspout above the diverter needs to be sealed with some tape. The connection does not need to be super water tight but does need to prevent water from escaping due to the restriction that the diverter has on the downspout. This happens during a heavy down pour.

Step 5: Simple Reliable Garden Hose Connections

Regular garden hose is designed to for pressures exceeding 100psi. In this application the pressure is unlikely to exceed 1psi so it provides very reliable connections between the barrels and the downspout diverter. The connection from the diverter requires a hose with two female connections, I used a connection hose from a washing machine because it is a good length and it has two female ends. I used the cheap rubber connection hoses that came with the our washing machine. You will also need a small extension hose to connect the tee to the rain barrel.

It is also handy to use a hose tee with shutoffs so you can isolate barrels, watering hose or the diverter. Multiple barrels can be added using additional tee connections. Larger 5/8" hose connections may increase the water capturing efficiency but you will need all of the components including the connection to the barrel to be 5/8" in order to achieve the added efficiency. I am sure the small diameter of the hoses I have used restricts the fill rate somewhat but after a rain event the barrel is usually full.

Step 6: Advantages

- Barrels will not overflow

- Barrels do not need a large hole in the top for water intake

- Barrels do not need a large hole in the side for overflow

- Easy to expand to use more barrels (add tee and extension hose)

- Can be implemented with common garden hose hardware designed for higher water pressure (reliable)

- Rain barrels can be positioned away from the downspout with a long hose running on the ground.

- Water is not exposed to mosquitoes

- The tee has a built in valves that can be used to isolate barrels

The bottom filled design takes away the need to have an always down pathway like a stream from the downspout to the rain barrel. Rain barrels no longer need to be located near downspouts so they can be positioned out of sight and away from buildings. Rain barrels can be positioned at a higher point on the property by moving the diverter higher on the downspout eliminating the need for a stand. Each barrel requires only a small hole at the top to allow air in and out and a male hose connection at the bottom. This greatly reduces what needs to be done to a barrel to use it as a rain barrel.