SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Well, here goes... One of my lawn zones is fairly large, and includes 12 heads. There is a very slight slope, mostly flat to the naked eye, but it does drop 2-3 inches from the highest point of the zone to the lowest sprinkler head in the same zone. After the zone shuts off, my lowest head leaks water. I've dug it up and there is no leak per se, it just comes out of the top of the head. If I raise the head about 3 inches (after dug up), the leaking stops. BUT the next lowest head then starts to leak. Because the zone is large, there is a lot of water in the line after the zone shuts off that wants to leak to the lowest point.
Is there any way to prevent this? The problem is, it's not a little water, it turns about a 5x5 foot patch of my lawn into an absolute marsh.