Sewer Pipe Flow Capacity Calculator
ANA›Life Services Authority›National Calculator Authority›Sewer Pipe Flow Capacity Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
Sewer Pipe Flow Capacity Calculator
Calculate the flow capacity of circular sewer pipes using Manning's equation. Supports full-flow and partial-flow (depth-based) conditions.
Pipe Diameter (mm)
Pipe Slope (m/m)
Manning's Roughness Coefficient (n)
Typical values: Concrete=0.013, PVC=0.009, Clay=0.013, Cast Iron=0.012
Flow Depth (mm) — leave blank for full-flow
Calculate
function sewCalc() { const resultDiv = document.getElementById('sew-result'); resultDiv.style.display = 'block';
const D_mm = parseFloat(document.getElementById('sew-diameter').value); const S = parseFloat(document.getElementById('sew-slope').value); const n = parseFloat(document.getElementById('sew-manning').value); const d_mm = document.getElementById('sew-depth').value.trim();
// --- Validation --- if (isNaN(D_mm) || D_mm ⚠ Please enter a valid pipe diameter (mm).'; return; } if (isNaN(S) || S ⚠ Please enter a valid slope (m/m), e.g. 0.005.'; return; } if (isNaN(n) || n ⚠ Please enter a valid Manning's n value, e.g. 0.013.'; return; }
const D = D_mm / 1000; // convert to metres const R_full = D / 4; // hydraulic radius for full circle = A/P = (πD²/4)/(πD) = D/4 const A_full = Math.PI * D * D / 4;
// Full-flow velocity and discharge (Manning's equation) // V = (1/n) * R^(2/3) * S^(1/2) // Q = V * A const V_full = (1 / n) * Math.pow(R_full, 2/3) * Math.pow(S, 0.5); const Q_full = V_full * A_full;
let partialHTML = ''; let depthWarning = '';
if (d_mm !== '') { const d = parseFloat(d_mm); if (isNaN(d) || d ⚠ Flow depth must be a non-negative number.'; return; } if (d > D_mm) { resultDiv.innerHTML = '⚠ Flow depth cannot exceed pipe diameter (' + D_mm.toFixed(0) + ' mm).'; return; }
const y = d / 1000; // depth in metres const ratio = y / D;
// Central angle theta (radians) subtended by the water surface // theta = 2 * arccos(1 - 2*y/D) const theta = 2 * Math.acos(1 - 2 * ratio);
// Partial-flow geometric properties const A_part = (D * D / 8) * (theta - Math.sin(theta)); const P_part = (D / 2) * theta; const R_part = A_part / P_part;
const V_part = (1 / n) * Math.pow(R_part, 2/3) * Math.pow(S, 0.5); const Q_part = V_part * A_part;
const q_ratio = Q_part / Q_full; const v_ratio = V_part / V_full;
if (ratio > 0.94) { depthWarning = '⚠ Note: Maximum discharge in a circular pipe occurs at approximately 94% full depth. Flows above this depth may be unstable.
'; }
partialHTML = Partial-Flow Results (depth = ${d.toFixed(1)} mm)
Flow Depth / Diameter Ratio (y/D)${ratio.toFixed(4)}
Partial Flow Area (Ap)${(A_part * 1e6).toFixed(2)} mm² | ${A_part.toFixed(6)} m²
Wetted Perimeter (Pp)${(P_part * 1000).toFixed(2)} mm | ${P_part.toFixed(4)} m
Hydraulic Radius (Rp)${(R_part * 1000).toFixed(2)} mm | ${R_part.toFixed(6)} m
Partial-Flow Velocity (Vp)${V_part.toFixed(4)} m/s
Partial-Flow Discharge (Qp)${Q_part.toFixed(6)} m³/s | ${(Q_part * 1000).toFixed(4)} L/s
Qp / Qfull${(q_ratio * 100).toFixed(2)}%
Vp / Vfull${(v_ratio * 100).toFixed(2)}%;
}
// Self-cleansing velocity check (minimum ~0.6 m/s recommended) let cleansingNote = ''; if (V_full ParameterValue Full-Flow Results Pipe Diameter (D)${D_mm.toFixed(1)} mm | ${D.toFixed(4)} m Pipe Slope (S)${S.toFixed(6)} m/m | ${(S * 100).toFixed(4)}% Manning's n${n.toFixed(4)} Full-Flow Area (Af)${(A_full * 1e6).toFixed(2)} mm² | ${A_full.toFixed(6)} m² Wetted Perimeter (Pf)${(Math.PI * D * 1000).toFixed(2)} mm | ${(Math.PI * D).toFixed(4)} m Hydraulic Radius (Rf)${(R_full * 1000).toFixed(2)} mm | ${R_full.toFixed(6)} m Full-Flow Velocity (Vf)${V_full.toFixed(4)} m/s Full-Flow Discharge (Qf)${Q_full.toFixed(6)} m³/s | ${(Q_full * 1000).toFixed(4)} L/s ${partialHTML}
`; }
#### Formulas Used
Manning's Equation (Full Flow):
V = (1/n) × R2/3 × S1/2
Q = V × A
Where:
- V = flow velocity (m/s)
- n = Manning's roughness coefficient (dimensionless)
- R = hydraulic radius = A / P (m)
- S = pipe slope (m/m)
- Q = volumetric flow rate (m³/s)
- A = cross-sectional flow area (m²)
- P = wetted perimeter (m)
Full-Flow Circular Pipe:
- Af = πD² / 4
- Pf = πD
- Rf = D / 4
Partial-Flow Circular Pipe (depth y):
- Ap = (D² / 8) × (θ − sinθ)
- Pp = (D / 2) × θ
- Rp = Ap / Pp
#### Assumptions & References
- Maximum discharge in a circular pipe occurs at approximately 94% of full depth (y/D ≈ 0.94), not at full flow, due to the reduction in hydraulic radius near the crown.
- Maximum velocity occurs at approximately 81% of full depth (y/D ≈ 0.81).
- Recommended minimum self-cleansing velocity: 0.6 m/s (AS/NZS 3500, EN 752).
- References: Chaudhry, M.H. (2008) Open-Channel Hydraulics; AS/NZS 3500.3; EN 752; ASCE Manual of Engineering Practice No. 36.
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