When my mom came to help me with my patio (back story on her blog, yes my mom has a blog now www.malibu566.blogspot.com) she also happened to break a sprinkler pipe. It was a pipe that had just been capped off and she assured me it wasn't active and it wouldn't make a difference if she just covered it with the sand and stones. Fast-forward to the next morning. I called her to see that she made it home safely because she had left before I was even awake. At this point she told me the sprinkler line was active, the stones had shifted slightly underneath and I had to fix it. Sprinklers aren't really my forte so I went to the hardware store and bought one of everything I thought might work.

Turns out this is all I needed. It only took about five minutes to repair and now the patio is beautiful again and no more shifting has occurred.