Water-Supply Diameter Selection

Size a water-supply pipe by pressure drop, or pre-size for a pump flow and verify the resulting velocity and pressure drop.

Size by pressure drop

Recommended velocity 1.2–2.0 m/s on mains; pressure drop 0.3–0.5 kgf/cm² (3–5 m head) per segment.

Flow velocity (m/s)

Pressure drop (kgf/cm²)

Pipe length (m)

Calculated diameter

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Design flow

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L/s

Design flow

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m³/h

Verify pressure drop for a pump flow

Enter the nominal diameter; if the computed value turns red, increase the diameter, if it turns green the size is acceptable.

Design flow (m³/h)

Nominal diameter (mm)

Pipe length (m)

Velocity

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m/s

Pressure drop

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kgf/cm²

Diameter verdict

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Size by drop: D = √(72·v·L / Δp) mm; design flow Q = ((D/100)·0.01·D)… = ((D·0.01)/2)²·π·v·10 (L/s), ×3.6 = m³/h. Verify: v = 354·Q/D² (m/s); Δp = 72·v·L/D² (kgf/cm²); green when 0.3–0.5 kgf/cm², otherwise enlarge the diameter.