All of the following factors affect sprinkler system precipitation rate except:

• A. Wind
• B. Sprinkler spacing
• C. Water pressure at the sprinkler
• D. Water source

Answer: (D)

Precipitation rate is the amount of water applied to the ground per hour by a sprinkler, and it’s determined by what the sprinkler head discharges at the operating pressure. The nozzle design fixes how much water comes out, and the pressure pushing water through that nozzle sets how fast it flows. Wind can move droplets and change where water lands, so it creates variability in coverage but doesn’t change the actual discharge leaving the nozzle. Sprinkler spacing affects how the wetting patterns from different heads overlap, altering uniformity and the effective rate across the area, even though each head’s discharge stays tied to its nozzle and pressure. Water pressure at the sprinkler is a direct influence: higher pressure increases the discharge rate and can raise the precipitation rate up to the head’s design limit.

The water source matters for whether the system can maintain the required pressure and flow, but it does not itself set the per-sprinkler precipitation rate. If the source can’t sustain the needed pressure, the rate can drop, but the source isn’t the variable that defines the rate in normal operation.