We noticed that part of the lawn was not only never drying out, but getting soggy enough to make mud when the kids walked through it. I couldn't see drips above ground, so I assumed it was leaking farther underground and soaking the surrounding area. When I went to dig out around the bad sprinkler head, it was extremely mucky and wet. Wish I had gotten to it sooner! Probably gave my tree a nice deep watering, though. :) I cleared the dirt all the way down to the riser and about 1 inch below, and about 9 inches on all sides. Keep the extra dirt on a tarp next to the hole, it makes it a lost easier to get back in when you're done and leaves less of a mess.
Sure enough, the riser was cockeyed and it looked like I had maybe not threaded it on there properly in the first place. It had probably been leaking the several years since it's installation, just not reaching the surface until recently. At this point I got to use my new trick, it's very simple and I am kicking myself for not thinking of it years ago:
If you hook together four right-angle street elbows, you get an articulated arm that allows you to adjust the height and placement of your sprinkler head quickly and easily. Just make sure you tighten the elbows to each other about 4/5ths tight, attach them to the line first, THEN attach the sprinkler head to the articulated riser, and you can adjust it from there. Don't forget to use thread tape, PTFE or Teflon tape. Once you have the head on, remove the top, leaving the housing attached to the line, and flush the system. Put the head back in the housing and you are good to go.
