TradesHow this works
Every irrigation zone has to run inside the flow your water supply can deliver. Measure that available flow, take how much each head draws, and the number of heads a zone can hold is just one divided by the other, with a little margin left so pressure holds at the heads. Your total head count then tells you how many zones the controller needs.
Do not pack a zone to the last drop of flow, and never mix sprays and rotors on the same valve. Leave a head of margin for a hot week or a clogged nozzle, and confirm the meter and service line can actually supply the flow you measured.
Common questions
How do I measure my available GPM?
Do a bucket test at the point of connection. Open the supply fully, time how many seconds it takes to fill a 5-gallon bucket, then divide 300 by the seconds. Thirty seconds means 10 GPM. This is the flow every zone has to live within.
How many heads can I put on one zone?
As many as your flow supports: the usable flow divided by the flow each head draws. If that gives 5, put 5 heads on the valve, not 7. Overloading a zone drops the pressure and every head waters short.
Can I mix sprays and rotors on one zone?
No. Spray heads and rotors apply water at very different rates, so on one zone some areas flood while others stay dry. Keep one head type per zone, and give each type its own run time on the controller.
Sources: Irrigation zoning: max heads per zone = available GPM / head GPM with a pressure margin; 5-gallon bucket flow test; typical head flow ranges (Rain Bird / industry).. Engine version 1.0.0. Risk tier 1.