Direct from Rainbird

Here is a link that might be useful: Rainbird

Thanks, I'll follow that up even give them a call to ask if I should try different sprinkler heads or not.

Sharon

hoyess, one inch of rain/irrigation per acre = 27154 gallons of water. 2.0 on the sprinkler nozzle indicates 2.0 gallons per minute. The area is 1018 sq.ft. (circle of 36 feet diameter). About 634 gallons are needed to provide one inch of irrigation to this area. 1018/43560 times 27154. The system is run for 90 minutes - 180 gallons. The heads are spaced to provide 100% overlap which means that in fact 360 gallons are applied to this area whenever it is irrigated. You can try stopping down the radius of the the existing heads to 27 ft. This would allow a 50% overlap which is a standard for good design. Still,the indications are that the system now requires a major maintenance check. It is a 'moderately difficult' DIY project.

hoyess, CORRECTION CORRECTION CORRECTION
I made an elementary mistake in the calculations.
The area is 4073 sq.ft. (circle of 36 feet RADIUS!). About 2536 gallons are needed to provide one inch of irrigation to this area. 4073/43560 X 27154. The head is putting out 180 gallons on an area that is supposed to get 2536 gallons! Bearing in mind that there is 100% overlap, this figure becomes 360 gallons based on the spacing of the heads. If the head is not doing a full circle coverage, the math has to be adjusted again.
My math teacher would be so disappointed; please do not tell him.