Collecting the rain shed by your roof for watering your yard and garden helps save money on your water bill. Normally, the water comes down the gutter and drains to an area that needs moisture the least--an issue easily remedied with a rain barrel. Whether you make your own rain barrel or purchase a complete rain collection system, it is necessary to hook it up to your gutter downspout. Hooking it up properly lets the rain flow in while keeping the water free from pests like mosquitoes.
Create an elevated base for the rain barrel beneath the downspout. Use a layer of bricks or concrete cinder blocks. An elevated barrel drains more easily when it's time to use the water inside.
Remove the existing downspout from your gutter. Pull off the spout if it is friction-fitted, taking care not to pull down the whole gutter system. Look for a retaining pin along the side and pull it out first, if necessary.
Purchase a flexible plastic downspout from a home improvement store. Slide it onto the gutter connection and reinstall any retaining pins, if applicable.
Alternately, measure the distance from your gutter to the lid of your rain barrel when it is sitting on the base. Purchase a length of gutter that meets this measurement and a downspout elbow piece. Attach the elbow to the downspout, then attach the downspout to the gutter.
Set the rain barrel on its base. Push the end of the flexible spout or the elbow into the corresponding cutout in the lid of the barrel.