your problem seems to be more a matter of the flow rate than pressure. if your system has a flow rate of 17 gpm at the source but your total heads per zone are trying to draw 25 gpm the water volume just is not there. your pressure is fine for spray heads but i'm afraid you may have to redesign with water volume in mind.

Thanks. It seems like that's exactly the problem. looking at rating for my sprinkler heads they use more than 17gpm. What's the typical gpm that people get. At a bib closest to the water meter I get about 22gpm. Valves are about 150ft away and connected by a 3/4 pipe

first, what size is your water source line? second. after checking some charts it may be possible to fix most of your trouble by repiping from your source to your valves with 1" pvc pipe. this will give you a higher flow rate and less friction loss so your pressure at the heads should rise 2-5 psi.

Thank you again. Do you think 2-5psi rise will make a difference. In order for me to run a new line I'd have to cut concrete driveway which can turn too expensive. It might be cheaper to just add two more zones. Would be ridiculousto use 5 zones for a 1500 sq ft. lawn.

The system was designed with full overlap. meaning each sprinkler shoots all the way to the next sprinkler.

To tested my theory I took one of the sprinklers off and put on a pressure gauge. At 9 remaining sprinklers running i was getting about 20psi when I turned few off and had only 5 running i it to about 35-40psi and at that point I could clearly see an increase in coverage.

Looking at the heads chart my 12ft head shoots about 10ft radius at 20psi. it also uses 2.1gpm I have 6 360 heads and 4 180. looking at the same chart at 20psi they use about 16.8gpm and I have 17gpm. so the amount of water should be sufficient.

then as i said, it looks to be more of a time issue. if you have had a longer, hotter stretch of time like my area evaporation will take more water out of the soil then you might think so increasing your run times or adding a second start time is the best thing you can do. i'll bet you will see some signifagant improvement in two weeks with no other changes to the system.

MrHIrrigation, thank you for all the feedback. here is what I tried with time. it's running at 5am and 5:30am 4 minutes each (meaning 8 minutes total) 4 times per week. I had it running every day but was getting mushrooms growing in other parts of the lawn but still had the same brown spots.

What would be your suggestion for time. I am in southern California LA area.

not knowing your exact weather patterns my best recomendation would be doubleing your times to 8min. with starts at 12:30am and 5:00am. that should give the soil time to absorb as much as possible with minimum evaporation. 4 day's a week should still work and you should see some results fairly soon. another thing that will help is adding a bit more fertilizer then you can cut back the water in a couple of weeks.

I am going to throw out an idea. If you are using older style nozzles Volume is the issue so using nozzles that use less volume per minute usually works. The sprinkler body can be left just a nozzle change.2 types of nozzles are hunter mp and toro precision they apply heavier droplets you run about twice the length of time and generally save about 30% in water. Hope it helps.