Tank to Pump

Nozzles & Equipment

Automatic Nozzle

An automatic nozzle is a fog nozzle whose internal baffle keeps the flow up near rated across a range of delivered pressures — the tip pressure tracks what you deliver, it is not pinned to a target. Pump it to its design tip pressure — about 100 psi — plus the line's friction loss.

Schematic of an automatic fog nozzle with a spring and a sliding internal baffle feeding a stream cone, beside a small flow-versus-pressure plot whose blue curve holds near a dashed rated-flow reference across the operating band and then drops away below a marked minimum operating pressure, where the cone collapses; the tip pressure tracks the delivered pressure rather than being pinned to a target.

Automatic nozzle · interactive

HOLDING88 psi tip · 136 gpmAbove the minimum operating pressure the baffle trims the orifice to keep the flow up near rated, so the stream stays usable even as the delivered pressure changes. The tip pressure just tracks what you deliver — automatic does not pin the pressure or buy free reach; it holds a workable flow across a range.

  • Delivered pressure88
  • Tip pressure88
  • Flow136

Above its minimum operating pressure of 75psi the baffle slides to keep the flow up near rated, so the stream stays well-formed across a range of delivered pressures — the tip pressure just tracks what you deliver (the panel reads the same), and the nozzle's 100psi design target is what it is rated for, not a pressure you get for free. Below that, the baffle bottoms out: the flow sags with the supply (the same starved flow law the simulator uses) and the pattern falls apart. These are training estimates; follow your SOPs and the nozzle's own data.

Drag the delivered pressure: inside the operating band a sliding baffle keeps the flow up near rated (HOLDING) while the tip pressure tracks what you deliver, but below the minimum operating pressure it bottoms out and the flow and pattern collapse (STARVED).

Because the baffle self-adjusts, an automatic nozzle keeps making a good-looking stream even when it is starved, continuing to produce a usable cone down to roughly 75 psi. That convenience hides a trap: the stream looks right even when the line is under-pumped.

So with an automatic nozzle the panel, not the nozzle, is the source of truth. Set the pump discharge pressure from the math — target tip pressure plus friction loss plus elevation — and do not let a healthy-looking stream talk you out of it.

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