Question
I have to run my irrigation off the city water. I need to figure out how many gallons per minute i have in order to figure how many heads i can put on a zone..... Thank you

Answer
William,
I'm very sorry for my late response. It has been very busy in my business lately.
To determine the GPM available you need to know the water service size (incoming pipe) and the meter size. The pressure is also helpful.
General "rule of thumb".
3/4" service with 5/8' meter   = 9-11 GPM
1" service with 5/8" meter     = 12-15 GPM
1" service with 1" meter      =  16-20 GPM
(5/8" and 3/4" meter are the same)
If your pressure is below 50# deduct 20% from these numbers
Hope this helps.

Matt