Question
I recently had outdoor sprinklers installed. When they are turned on the pipes shake and knock. Also when they are turned off water shoots out around the pressure/syhphon housing. Is this normal?

Answer
This sort of thing can have several causes, but I would suspect in your case that the cause is that the supply line to the sprinkler valves is larger than the valves and/or the pipe just downstream from the valves.  The differance in pressure can cause the pipes to shake and rattle.  You can try several things: 1. If you have a gate valve in the supply line before the valves, try adjusting it (usually closing a little); 2. Try adjusting the flow control on the sprinkler valves, opening it as much as you can but so that they will still shut off; 3. If these dont work, you may need to install a pressure relief valve on the supply line to the sprinkler valves.