Quick Answer
Redirecting downspouts effectively for rain collection involves connecting them to a rainwater harvesting system, which typically includes a collection tank and a first flush device to prevent debris from entering the tank.
Designing the Redirected Downspout System
When redirecting downspouts, it’s essential to consider the flow rate of the downspout and the size of the collection tank. A good rule of thumb is to connect a 2x3 inch or 2x4 inch downspout to a 275-gallon collection tank, assuming a moderate rainfall of 0.5 inches per hour. The downspout should slope gently towards the collection tank, with a minimum slope of 1/8 inch per foot to ensure a smooth flow.
Installing the First Flush Device
The first flush device is a critical component in any rainwater harvesting system, as it prevents debris and contaminants from entering the collection tank. A typical first flush device consists of a diverter valve and a screen. The diverter valve should be installed at the base of the downspout and should be designed to shut off the flow of water after the first 10-20 gallons have flowed through the downspout. This allows any debris and contaminants to be washed away, leaving clean water to flow into the collection tank. The screen should be installed above the diverter valve to catch any larger debris and prevent it from entering the system.
Connecting the Downspout to the Collection Tank
Once the first flush device has been installed, the downspout can be connected to the collection tank. The connection should be made using a 3-inch or 4-inch PVC pipe, which should be sized according to the flow rate of the downspout. The pipe should be sloped gently towards the tank, with a minimum slope of 1/8 inch per foot, to ensure a smooth flow. The connection should also be secured using a PVC elbow and a slip joint, to prevent any leaks or water damage.
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