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To determine how long to run your sprinklers, place several empty, straight-sided cans or cups at different distances within one zone. (Uniform coffee mugs work well.) Run the sprinklers for 15 minutes and measure the amount of water collected in each can. Calculate an average water depth and determine how long it will take to apply a Â½ to Â¾ inch of water. Example: Â· Â¼â average depth of water after 15 minutes â water 35-50 minutes in that zone. Â· Â½â average depth of water after 15 minutes â water 20-30 minutes in that zone.
The number of sprinklers per zone depends on the pounds per square inch pressure (PSI) and gallons per minute (GPM) flow of the system as well as the gallons per minute used by each sprinkler head.Sprinkler heads use more gallons per minute at higher PSI but can be spaced farther apart.. Measure GPM, or gallons per minute flow, by placing a 5-gallon bucket under the faucet. Turn the faucet on and record how many seconds it takes for the bucket to fill. Calculate GPM by dividing the number of gallons (5) by the number of seconds and multiplying by 60.