Once your sprinklers are clean and in place, flush the system. Screw a flush cap (which helps keep pressure high) onto your first sprinkler and turn on the water for 15 to 20 seconds, then repeat ...

It's the area where the sprinkler company blows out excess water in the fall. You will need a flathead screwdriver. Turn a quarter of a turn so they are against the pipe, which means they are closed.