Water-Supply Pipe Sizing & Head Loss
Design second-flow from sanitary-fixture equivalents (Ng), automatic nominal-diameter selection, velocity check and frictional head loss.
| No. | Start | End | Length L (m) | Toilet | Urinal | Bidet | Shower | Bathtub | Washer | Lavatory | Kitchen sink | Floor drain | Seg. Ng | Cum. Ng | Design flow (L/s) | Nominal DN | Calc dia (mm) | Velocity (m/s) | Seg. loss (m) | Total loss (m) | Cum. loss (m) |
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Max velocity
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m/s
Total cumulative loss
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m H₂O
Design second-flow q = min(0.2·α·√Ng, 0.2·Ng) with α=1.1. Fixture equivalents (Ng): toilet 0.5, urinal 0.5, bidet 0.5, shower 0.75, bathtub 1.2, washer 1.0, lavatory 0.75, kitchen sink 1.0, floor drain 1.0. Computed inner diameter selected from GB standard sizes (steel 管材规格). Velocity v = 4000·q/(π·dj²); head loss per 1000 m by Hazen–Williams (or PP-R Colebrook-style); segment loss = hf·L/1000·(1+local factor) with local factor 0.3.