When you turn your sprinkler system it is important to be careful with how you go about it.  Most all systems have, or at least should have, a ball valve located somewhere between the water meter and the vacuum breaker of the system.  This is the U shaped thing that comes out of the ground and is typically made of copper or plastic. The water line should be empty and full of just air.  When you turn your system back on, if you open the valve too fast you can create what is called a “Water Hammer”. This is when the force of the air or the wall of water hits the pipes or any other connection so hard that it causes damage to the equipment.  The proper way to handle this would be to slowly turn the water on and allow the air to escape. Even after you open the system up don’t be surprised if it blows a lot of air from the lines for several minutes. On another note, I’d be careful just sticking my hand into any of these boxes without first looking and making sure there are not any critters living in there.  We have found everything from spiders to snakes and even scorpions. Hope this helps!