If your contractor is installing funny pipe for your main lateral lines for your sprinklers, you need to stop work ASAP and go over the entire installation. Better check the plumbing from your POC (Point of Connection) all the way out. Like Wetboots said, I hope there is a backflow device installed. For the pressure, I would be installing at least 1" line for your sprinklers. You can come off of that line with your funny pipe to your sprinkler heads, but DO NOT use funny pipe for the entire system. Time to have a sit down with your contractor.
Tony Posey
Ridge Run Landscapes