I have a 3 zone sprinkler system. One irrigates the front lawn and use gear type sprinklers. The second one irrigates the back and side lawns and uses spray type sprinklers. The third is the drip system and irrigates the back and front flowers and shrubs. I have a leak from the lowest front lawn sprinkler but only when the drip system is running. I can't figure out why a sprinkler on a totally different zone would leak. Any ideas?