Worked examples
Long-form design walkthroughs that thread multiple PE-Calc tools end-to-end on real-world problems. Each example shows the governing equations, realistic numbers, plan-review gotchas, and links to the live calculators so you can swap in your own site data.
Driveway Culvert (25-yr Storm)
Tc → Rational → HDS-5 inlet/outlet control → outlet velocity check
24-inch RCP Partial Flow
Circular-pipe geometry, y/D iteration, self-cleansing velocity check
Commercial Parking Lot
Composite C, TR-55 Tc, 10-yr peak Q, first-pass inlet layout
Composite Curve Number
Area-weight CN (not Q), 2.5-in storm runoff depth and volume
6-inch PVC Water Main
Hazen-Williams friction + minor losses, residual pressure check
36-inch CMP Road Crossing
HDS-5 inlet vs outlet control, HW/D limit, outlet riprap
Photo-Sieve Grain Size
113 grains from a coarse-sand photo; D₅₀ = 1.68 mm, σ = 0.54 φ
Trapezoidal Grass Channel
Normal depth for 60 cfs, velocity + shear + freeboard checks (HEC-15)
24-inch CMP vs RCP
Same pipe, half the capacity — the roughness story with upsizing options
12-inch Steel Water Main
Friction at C=130 plus the aging sensitivity from C=140 to C=100
Detention Pond Orifice
48-hr drawdown sizing, exact falling-head math, the half-head mistake
90° V-Notch Seepage Weir
Dam toe-drain monitoring rating: Q = 2.48·H^2.5 + installation rules
Need a quick lookup table instead of a full walkthrough? Browse the printable reference cards — Manning's n, curve numbers, weir coefficients, and more on one letter page each.