Thanks for all your help.
I have a separate meter for irrigation, and it probably has a bigger feed than the meter for the house. I doubt I’m getting 35 gpm in the house. The house meter incurs sewer charges based on the amount of water used. The irrigation meter has no sewer charges.
I think I’m going to have to redo the entire system. The mains use crappy thin schedule 200 pvc and the few heads I dug up are connected with that old black poly pipe. Ugh.