Pump Head → Pressure

What should the discharge gauge read for a given head?

Fluid temperature °F

density lb/ft³ · SG

Plant fluids are water — CHW ≈ 45 °F, condenser ≈ 85 °F, HHW ≈ 120–200 °F. Hotter water is lighter, so the same head is slightly fewer psi.

💧 Expected discharge pressure

Pump head (feet, off the curve)

Suction pressure (gauge)

psi

Developed (differential)

— psi

Discharge gauge should read

— psi

🔎 Field check — head from the gauges

Read both gauges to see the head the pump is actually making — compare to the curve.

Discharge pressure

psi

Suction pressure

psi

Differential

— psi

Developed head

— ft

psi = head (ft) × density (lb/ft³) ÷ 144 · ≈ head × SG ÷ 2.31 for water. Head from the pump curve is total dynamic head; the discharge gauge = suction + that.