As water becomes increasingly scarce in many places, many people are turning to old-fashioned rain barrels to collect water for yards and gardens. These can be elaborate and expensive with built-in spigots and stylish accents designed to complement the architecture of your home, or as simple as a recycled 55-gallon drum or large trash you can dip water from by removing the lid. If you prefer to put your money in the garden instead of fancy gadgets, make your own rain barrel from scratch.
Obtain a suitable large container --- 55-gallon barrels are often available from local fast-food places for free or reduced charge, but they can be purchased new or used from online sources or local companies as well, so check around. Be sure the original use was food-grade before turning it into a water source for the garden.
Install guttering and downspout on your roof edge as per manufacturer's instruction (if you do not already have them). Locate your gutter on the side of the house on which you will place the rain barrel --- preferably close to the garden.
Ensure the barrel has a tight-fitting lid to keep out mosquitoes or small children. Purchase and install a device designed to deter raccoons from removing trash-can lids if necessary.
Position your barrel below the downspout with the end of the spout a foot or so above the lid --- allowing room to clear away leaves and remove the lid from the barrel when necessary. Add a leaf strainer to the end of the downspout.
Cut a hole in the lid about the size of a dinner plate with a jigsaw. It need not be round --- square will work fine, too --- just ensure that it is large enough to handle the volume of water from the downspout in a heavy rain.
Cut a piece of fiberglass screening (for windows) about 1 inch larger all the way around than the hole cut in the lid. Cut a piece of thin gasket material (rubber, cork, metal flashing or thin plastic sheeting --- whatever is handy, and capable of holding the screen in place without breaking or tearing) into a ring about 1 inch wide and the same shape and size as the fiberglass screen.
Drill holes every few inches through the gasket material, screen and lid together, then fasten the gasket and screen to the lid (gasket uppermost) by running short bolts through from the underside. Place a wide metal washer over the end of each bolt, followed by a lock washer and nut on the top; tighten. This screened hole serves to keep mosquitoes out while allowing water in.
Use a spade bit to drill a hole precisely the diameter of a scrap section of garden hose about 1 inch from the top of the barrel and to one side. Smooth rough edges with sandpaper. Run the cut-off end of the garden hose from the inside of the barrel through the hole and out the other side, allowing the hose coupling to act as a stop to prevent it being pulled all the way through. Run the unattached end away from the house --- preferably to the garden or second containment system --- to act as an overflow valve when the barrel is full.