Question
Matt,
I had to replace a RainBird rotor sprinkler (5000 Series) due to a broken cover.  I replaced it last night, screwed on the new sprinkler, and started it up to check for leaks.  Once the system had the water pressure the sprinkler head came up and worked fine; however, a couple inches of water filled the hole around the new sprinkler.  I ran it for a couple of minutes and it seemed to stop getting deeper.  I shut off the sprinklers and let it sit over night to see if the water would drain or if it would stay wet due to a constant leak.  This morning the hole was dry.  I started it back up and the same thing happened.  Is this a true leak, someway to bleed off pressure, or do I need to try and re-install the sprinkler?
Thanks for your help,

Answer
Thanks for your question.
I sound to me as if you have a leak at the threads of the sprinkler. You may want to dig-up the sprinkler and watch where the water is coming from. The other possibility is, in the process of changing the sprinkler you allowed a little soil into the riser and or threads. This soil inside the sprinkler can make the seal leak and cause the same problem. If this is the case you would see water running out of the top of the sprinkler.
I hope this helps.

Matt