Question
My sprinkler system works pretty well, however, after it runs it's cycle and shuts off there is a very loud BANG in the pipes both outside by the automatic valve and in the basement in the overhead pipes.  I have had the top of the automatic valve crack twice now and leak water all over the place outside.  What is the cause of this BANG and how can I fix it to not do that anymore?

Answer
It referred to as "water hammer". You probably have great water pressure which amplifies the problem. It's caused from the water going extremely fast through the pipe, then the valve closes quickly the water stops suddenly. bang!!! (your washing machine does this also, just on a smaller scale)
A simple fix to try is to limit the water going to the sprinkler system. Do this by partially closing the main water supply valve. If this helps then I would suggest a pressure reducing valve (PRV)on the main supply line to the sprinklers. Another fix, though I'm not fond of it, is to install a pressure tank on the irrigation system. The problem with this is your using the tank for the wrong purpose and it usually fails sooner.
There are many options, let me know what type of irrigation valves you have. There might be alternatives to these suggestions.

Matt