Sewage Pipe Hydraulics & Invert Design
Non-full circular sewage pipe by Manning (UPVC n=0.009): velocity & capacity, automatic diameter selection with too-slow/too-big/too-small checks, and successive invert-elevation derivation.
| No. | Length L (m) | Local Q (L/s) | Through Q (L/s) | Design Q (L/s) | Diameter D (mm) | Fill h/D | Slope i | Velocity v (m/s) | Wet area A (m²) | Hyd. radius R (m) | Capacity Q (L/s) | Drop ΔH (m) | Invert ↑ (m) | Invert ↓ (m) | Water ↑ (m) | Water ↓ (m) |
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Max velocity
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m/s
Min velocity
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m/s
Design flow ΣQ
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L/s
Capacity ΣQ
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L/s
θ = acos(1−2·h/D). Wet area A = (θ − √(4t−2t²)·(1−2t))·D²/4 when t<0.5, or (π − θ + √(4t−2t²)·(1−2t))·D²/4 when t>0.5; hydraulic radius R = A/(θ·D/1000); velocity v = R^(2/3)·√i/n. Capacity (L/s) = v·A·1000; verdict: 1 < vA/E < 1.1 ok, >1.1 too big, <1 too small. Invert: start of row n = terminal of row n−1 + (D₋₁−D)·0.001; water surface = invert + h/D·D·0.001. Max fill 0.55 (200–300), 0.65 (350–450), 0.7 (500–900), 0.75 (≥1000).