There are things to consider before installing a rain barrel. Because the rainwater you plan on harvesting is running off your roof, there are safety concerns. Some roofing materials will contaminate rainwater and make it dangerous to use. You should not use roof catchment areas that incorporate asbestos shingles, tar and gravel, or treated cedar shakes. You should also check your gutters to make sure that they don't use lead solder or lead based paints.
Once you know that you can harvest rainwater safely, you need to evaluate how much water you want to capture, and how you want your system to look. Although there are many different styles and designs available, a large aboveground system will take up quite a bit of space in your flowerbed and can get expensive, so it's important to understand what you want and have a budget in mind before you go shopping. You should ask yourself if you plan on watering your lawn, washing your car or maintaining your vegetable garden with your rainwater reserves. Activities like watering the lawn can consume lots of water, so do your homework. Check your water bills from last few summers to determine how much water you use during the peak summer months and plan from there.
Any system you select or build will need a tight-fitting lid to keep animals out and discourage the development of algae. It should also be made of quality material like food grade plastic that's UV protected and have a fine mesh screen to reduce the amount of debris in the water and keep mosquitoes from using the standing water as a breeding ground.
To keep the foundation of your home safe from water damage, it's important that your rain barrel have an automatic overflow mechanism that diverts water back into the downspout once the barrel has been filled or to an overflow hose that drains downhill away from your home.
Other considerations for convenience and water quality are water filtration systems, UV lights to kill bacteria and pumps to make water distribution easier. There are also special diverters available that will block the initial water flow in a rainstorm from going into the rain barrel. After the initial flow washes the dirt out of the air and off the roof, the diverter reroutes water back into the barrel.
Next up, we'll take a look at how to use a rain barrel.