Before digging your rain garden, you will want to perform a soil infiltration/percolation test to determine if you’ve chosen an area where water can easily soak into the ground.
Depending on the tools you have available there are a couple ways to conduct this test.
Method 1:
Step 1: With a posthole digger or shovel, dig a hole approximately 6 to 8 inches deep and 4 to 6 inches wide.
Step 2: Fill in the hole with water
Step 3: Wait… If the water has been completely absorbed after 6 hours, the site is ideal for your rain garden. If the water is completely absorbed between 6 to 24 hours, the site is suitable but you may still want to consider a better location. If there is water in the hole after 24 hours, then the site is unsuitable and you will need to find a new location.

Method 2:
Method 2 is slightly more involved but could make for a fun project with your young children.
Step 1: Procure an empty coffee can and with a can opener, remove the bottom so it’s open on both sides.
Step 2: Place the can at the testing site and put a board across the top, with a hammer or rubber mallet drive the can approximately 1 to 2 inches into the ground.
Step 3: Fill the can with water and wait.
Step 4: If the water has been completely absorbed after 6 hours, the site is ideal for your rain garden. If the water is completely absorbed between 6 to 24 hours, the site is suitable but you may still want to consider a better location. If there is water in the hole after 24 hours, then the site is unsuitable and you will need to find a new location.
