If you are in an area that gets a lot of rainfall you may need a drywell. A drywell is used to collect water that drains from your gutters. The following steps will teach you how to build your own.
Step 1 - Understand Where to Put the Drywell
The chief reason you want a drywell is to stop water from collecting in your yard or around the foundation. Choose an area that is away from the home and one that is preferably on a slight downward slope. Make sure the drywell location is in direct sight and centered to the downspout.
Step 2 - Dig Out the Drywell
When you have found the right spot, begin staking and stringing off the area. The drywell can be as large as you want, but to make it easier and less conspicuous, a 5x5 foot square will suffice. Use your shovel and begin scoring the perimeter of the staked out area. Excavate to a 12-inch depth and pack down the soil. Add a 4-inch layer of drainage stones on top of the packed dirt.
Step 3 - Dig a Trench
The pipe needs an out-of-the-way place to sit in, and it also needs to slope so gravity can work. Begin at your downspout and walk toward the drywell, staking every few feet. Once you reach the drywell run a string between the first and last stake, and then remove the others.
Use the spade and begin removing the dirt along this line. The trench should be dug to 6-inches wide, 12-inches deep, and span all the way to the drywell. For the water to move toward the drywell the trench needs to be sloped. Use the spade and gradually remove small amounts of dirt to create a very slight slope.
Step 4 - Adjust the Downspout
Since the downspout is already on an angle you need to bend it so the opening is straight toward the trench. Place a section of solid PVC pipe inside the downspout. Attach the PVC joint to that piece of pipe so when you add on another piece of pipe it will follow along the trench.
Step 5 - Place Pipe
The amount of solid pipe you need depends on the length of the trench to the drywell. Place a section of perforated PVC pipe at the end of the trench with a small bit of it poking into the drywell. Measure the distance from the PVC joint to the perforated pipe. This will determine how many solid PVC pipe sections are needed. Begin attaching the solid PVC pipe to the PVC joint and continue until it attaches to the perforated pipe.
Install the overflow valve according to package directions.
Step 6 - Add Finishing Touches
Place drainage stones under the perforated pipe section, followed by landscaper's fabric. Wrap the pipe end with the fabric and add more stones to cover the top. Fill the trench in with the soil that was removed previously and tamp it down.