The question "How do I get sprinklers to work?" gets asked so often, I decided to make a quick but clear tutorial.
Guide to Sprinklers
Step 1: Grid Placement On
The trick to setting up your sprinklers perfectly, is placing the plots with grid placement on and the sprinklers with grid placement on.
Go into your menu, click settings and check Grid Placement.
Step 2: Place the Plots
With grid placement on, it becomes rather easy to place well-aligned plots.
For this tutorial, I'll place one, two and four plots for a copper, silver and gold sprinkler respectively.
Step 3: Grid Placement Off
Go back into your settings and turn grid placement off.
Step 4: Place the Sprinklers
With grid placement off, you can hover the sprinkler over the spot until you see a sprinkler icon appear.
Icon up means the sprinkler will water that crop.
Same goes for silver sprinklers...
... and gold sprinklers.
No icon, no sprinkling!