Unclogging the downspouts is not a difficult job to accomplish, but is very necessary to do. You should inspect your downspouts at least once a year to make sure they are able to function and operate properly.
Step 1 - Remove the Downspout
Get up on a ladder and unhook the downspout from the gutter system. Then, lay the downspout on the ground.
If there are leaves or debris at the top or bottom of the downspout opening, just pull the junk out with your hands (remember, put on some protective gloves when doing this job because it can be messy and you never know what you will encounter when you remove the debris).
Step 2 - Push a Brush Through
Once you have cleared out the two sides to the openings, look through the downspout. If you still see debris inside the spout, then push a brush through starting on one end and then do the same on the other end.
Step 3 - Pressure Wash
Run the pressure washer (on a light setting) through the downspout. If you think the stream is still being disrupted by a clog, then repeat the steps until everything has been cleared away.