Four zones not working since startup

Hi, sorry for the long question, but I thought a little background was in order...

New member today, glad to be able to talk to you. I am Tony Magrady from Naperville, IL around Chicago. Professionals winterized my inground sprinkler system, and I turned it on in the Spring, same as last year. I turned the main valve on slowly, and did not see any leaks above ground. I am almost postive I waited until the ground was no longer frozen - it was late March. I had to get it going earlier than I usually do because I had to mark sprinkler heads and lines for a crew that was going to install our new patio soon after, and I did not want to miss any heads that I forgot and could not see. It was sort of a cool day. They had to move one or two lines, but that did not seem to be an issue.

The problem is that 4 out of the 9 zones I have no longer work. In each zone a lot of water burbles or gushes up around one of the heads instead of coming out of the head. My friend who is mechanically inclined told me he thinks I may be able to fix it in the valve control box, but I think there are leaks or disconnections in the lines or connections around the heads. What is your take on this?

If I am right, I'll start digging. Would I just need new PVC pipe and/or elbows? I'll try Home Depot for replacement parts, a home center at least in the Midwest, but if they do not have it, do you know what sort of places I should look up? Not sure if I should call my pros for parts because they might try to talk me out of doing it myself.

Thanks, Tony

Hard to say. If you're lucky, it'll just be one leak in your main line that feeds those 4 zones. If you're unlucky, you have multiple leaks and will have to do a lot of digging around to find them.

Thanks. So far, two heads that need to be replaced and one line that came separated from a connector. As long as I got the right size - not too tough.