Foundation Waterproofing Drainage Calculator

ANA›Life Services Authority›National Calculator Authority›Foundation Waterproofing Drainage 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; } }

Foundation Waterproofing Drainage Calculator

Calculate drainage pipe capacity, gravel backfill volume, waterproofing membrane area, and sump pump sizing for foundation waterproofing systems.

### Foundation Dimensions

Foundation Perimeter Length (ft)

Foundation Wall Height / Depth (ft)

Foundation Wall Thickness (in)

### Drainage Pipe

Drain Pipe Diameter (in)

4 inch (standard) 6 inch 8 inch

Pipe Slope (in/ft)

Manning's n (pipe roughness)

0.011 – Smooth PVC/HDPE 0.013 – Corrugated plastic 0.015 – Concrete pipe

### Gravel & Membrane

Gravel Trench Width (ft)

Gravel Trench Depth (ft)

Membrane Overlap / Extra (%)

### Sump Pump Sizing

Design Rainfall Intensity (in/hr)

Drainage Area (ft²)

Runoff Coefficient (C)

0.35 – Lawn / landscaped 0.50 – Mixed surface 0.70 – Paved / roof 0.90 – Impervious

Calculate

### Results

function fouCalc() { const errEl = document.getElementById('fou-error'); const resEl = document.getElementById('fou-result'); const outEl = document.getElementById('fou-output'); errEl.textContent = ''; resEl.style.display = 'none';

// --- Inputs --- const L = parseFloat(document.getElementById('fou-length').value); const H = parseFloat(document.getElementById('fou-depth').value); const wallIn = parseFloat(document.getElementById('fou-wall-thick').value); const dIn = parseFloat(document.getElementById('fou-pipe-dia').value); const S = parseFloat(document.getElementById('fou-slope').value); const n = parseFloat(document.getElementById('fou-manning').value); const gW = parseFloat(document.getElementById('fou-gravel-width').value); const gD = parseFloat(document.getElementById('fou-gravel-depth').value); const overlap = parseFloat(document.getElementById('fou-membrane-overlap').value); const iRain = parseFloat(document.getElementById('fou-rainfall').value); const A = parseFloat(document.getElementById('fou-drainage-area').value); const C = parseFloat(document.getElementById('fou-runoff-coeff').value);

// --- Validation --- const errors = []; if (isNaN(L) || L 0."); if (isNaN(H) || H 0."); if (isNaN(wallIn) || wallIn 0."); if (isNaN(gW) || gW 0."); if (isNaN(gD) || gD 0."); if (isNaN(overlap) || overlap 50) errors.push("Membrane overlap must be 0–50%."); if (isNaN(iRain) || iRain 0."); if (isNaN(A) || A 0.");

if (errors.length > 0) { errEl.innerHTML = errors.join(''); return; }

// ============================================================ // 1. PIPE FLOW CAPACITY — Manning's Equation (full-flow) // Q = (1/n) * A_pipe * R_h^(2/3) * S^(1/2) // For circular pipe flowing full: // A_pipe = π * d² / 4 // R_h = d / 4 (hydraulic radius) // Units: d in feet, S in ft/ft, Q in ft³/s → convert to gpm // ============================================================ const slopeFtFt = S / 12; // in/ft → ft/ft const dFt = dIn / 12; // inches → feet const A_pipe = Math.PI * dFt * dFt / 4; // ft² const R_h = dFt / 4; // ft const Q_cfs = (1 / n) * A_pipe * Math.pow(R_h, 2/3) * Math.pow(slopeFtFt, 0.5); const Q_gpm = Q_cfs * 448.831; // ft³/s → gpm const Q_lpm = Q_cfs * 28316.8 / 1000; // ft³/s → L/min (approx)

// ============================================================ // 2. GRAVEL BACKFILL VOLUME // V_gravel = L * gW * gD (ft³) // Subtract pipe volume: V_pipe = π*(d/2)² * L // Convert to cubic yards (÷ 27) // ============================================================ const V_gravel_gross = L * gW * gD; // ft³ const V_pipe_vol = Math.PI * Math.pow(dFt/2, 2) * L; // ft³ const V_gravel_net = V_gravel_gross - V_pipe_vol; // ft³ const V_gravel_yd3 = V_gravel_net / 27; // yd³ const V_gravel_tons = V_gravel_yd3 * 1.4; // approx 1.4 tons/yd³ for crushed stone

// ============================================================ // 3. WATERPROOFING MEMBRANE AREA // Area = L * H (perimeter × wall height) // Add overlap factor // Also add footing area: L * (wallIn/12) // ============================================================ const wallFt = wallIn / 12; const A_wall = L * H; // ft² const A_footing = L * wallFt; // ft² (footing face) const A_membrane_raw = A_wall + A_footing; const A_membrane = A_membrane_raw * (1 + overlap / 100); // with overlap const A_membrane_m2 = A_membrane * 0.0929; // ft² → m²

// ============================================================ // 4. SUMP PUMP SIZING — Rational Method // Q_runoff = C * i * A / 96.23 (ft³/min) // where i = in/hr, A = ft² // Convert to gpm: × 7.48052 // Add 25% safety factor for pump selection // Q_pump_gpm = Q_runoff_gpm * 1.25 // ============================================================ // Rational formula: Q (ft³/s) = C * i(in/hr) * A(acres) / 1 // A in acres = A_ft2 / 43560 const A_acres = A / 43560; const Q_runoff_cfs = C * iRain * A_acres; // ft³/s (rational method) const Q_runoff_gpm = Q_runoff_cfs * 448.831; const Q_pump_gpm = Q_runoff_gpm * 1.25; // 25% safety factor

// Recommend pump size (standard sizes: 1/4, 1/3, 1/2, 3/4, 1 HP) // Typical 1/3 HP sump pump ≈ 35 gpm; 1/2 HP ≈ 60 gpm; 3/4 HP ≈ 80 gpm; 1 HP ≈ 100 gpm let pumpHP = "1/4 HP (≈ 25 gpm)"; if (Q_pump_gpm > 100) pumpHP = "> 1 HP — consult engineer"; else if (Q_pump_gpm > 80) pumpHP = "1 HP (≈ 100 gpm)"; else if (Q_pump_gpm > 60) pumpHP = "3/4 HP (≈ 80 gpm)"; else if (Q_pump_gpm > 35) pumpHP = "1/2 HP (≈ 60 gpm)"; else if (Q_pump_gpm > 25) pumpHP = "1/3 HP (≈ 35 gpm)";

// ============================================================
// 5. PIPE ADEQUACY CHECK
// ============================================================
const pipeAdequate = Q_cfs >= Q_runoff_cfs;
const pipeStatus = pipeAdequate
? "✅ Pipe capacity is sufficient for design runoff.": "⚠️ Pipe capacity is insufficient — consider larger diameter or steeper slope.";

// ============================================================ // OUTPUT // ============================================================ const fmt = (v, d=2) => v.toLocaleString('en-US', {minimumFractionDigits:d, maximumFractionDigits:d});

outEl.innerHTML = `

Category Parameter Value

Drainage PipeCapacity Pipe Diameter ${dIn} in

Slope ${S} in/ft (${fmt(slopeFtFt*100,3)}%)

Full-Flow Capacity (Q) ${fmt(Q_cfs,4)} ft³/s

Full-Flow Capacity (Q) ${fmt(Q_gpm,1)} gpm

GravelBackfill Trench Volume (gross) ${fmt(V_gravel_gross)} ft³

Pipe Displacement ${fmt(V_pipe_vol)} ft³

Net Gravel Volume ${fmt(V_gravel_net)} ft³ (${fmt(V_gravel_yd3)} yd³)

Estimated Weight ${fmt(V_gravel_tons)} tons

WaterproofingMembrane Wall Area ${fmt(A_wall)} ft²

Footing Face Area ${fmt(A_footing)} ft²

Total Membrane (incl. ${overlap}% overlap) ${fmt(A_membrane)} ft² (${fmt(A_membrane_m2)} m²)

Sump PumpSizing Design Runoff (Rational Method) ${fmt(Q_runoff_cfs,4)} ft³/s (${fmt(Q_runoff_gpm,1)} gpm)

Required Pump Capacity (+25% safety) ${fmt(Q_pump_gpm,1)} gpm

Recommended Pump Size ${pumpHP}

Pipe Adequacy ${pipeStatus}

resEl.style.display = 'block'; }

#### Formulas Used

1. Pipe Flow Capacity — Manning's Equation (full-flow circular pipe):

Q = (1/n) × Apipe × Rh2/3 × S1/2

where Apipe = π·d²/4, Rh = d/4 (hydraulic radius for full circular pipe), S = slope (ft/ft), n = Manning's roughness coefficient.

2. Gravel Backfill Volume:

Vnet = (L × Wtrench × Dtrench) − (π·(d/2)² × L)

Convert ft³ ÷ 27 = yd³; weight ≈ yd³ × 1.4 tons (crushed stone).

3. Waterproofing Membrane Area:

Amembrane = (L × H + L × twall) × (1 + overlap%/100)

where H = wall height, twall = wall thickness (ft).

4. Sump Pump Sizing — Rational Method:

Qrunoff = C × i × Aacres [ft³/s]

Qpump = Qrunoff × 1.25 (25% safety factor) → convert to gpm (× 448.831)

where C = runoff coefficient, i = rainfall intensity (in/hr), A = drainage area (acres).

#### Assumptions & References

Foundation Waterproofing Drainage Calculator

Foundation Waterproofing Drainage Calculator

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References

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