Hi all, I'm new here and have a very ameteur question. Working with a pre-existing system that used all spray heads. Spray heads provide inadequate coverage (if at all), so I decided to try rotors. Got some small Rain Bird rotors, screwed them in, and now ... nothing. The head pops up, water squirts for a second (as if clearing the line), but it does not operate. What have I done wrong? Thanks for any and all suggestions.