Whole House Filtration System Size Calculator
ANA›Life Services Authority›National Calculator Authority›Whole House Filtration System Size 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; } }
Whole House Filtration System Size Calculator
Determine the correct whole house water filtration system size based on your household's peak flow rate demand, daily water consumption, and filter capacity requirements.
Number of Occupants
Number of Bathrooms
Daily Water Usage per Person (gallons)
Average US household: 80–100 gallons/person/day
Incoming Water Pressure (PSI)
Typical residential: 40–80 PSI
Main Supply Pipe Diameter (inches)
3/4 inch 1 inch 1-1/4 inch 1-1/2 inch
Water Hardness (GPG)
Grains per gallon (0–3 soft, 3–7 moderate, 7–11 hard, 11+ very hard)
Sediment Level
Low (clear municipal water) Moderate (slight turbidity) High (well water / visible particles)
Calculate
function whoCalc() { var occupants = parseFloat(document.getElementById('who-occupants').value); var bathrooms = parseFloat(document.getElementById('who-bathrooms').value); var usage = parseFloat(document.getElementById('who-usage').value); var pressure = parseFloat(document.getElementById('who-pressure').value); var pipeDia = parseFloat(document.getElementById('who-pipe').value); var hardness = parseFloat(document.getElementById('who-hardness').value); var sediment = parseFloat(document.getElementById('who-sediment').value); var resultDiv = document.getElementById('who-result');
// --- Validation --- if (isNaN(occupants) || occupants 20) { resultDiv.style.display = 'block'; resultDiv.innerHTML = '⚠ Please enter a valid number of occupants (1–20).'; return; } if (isNaN(bathrooms) || bathrooms 10) { resultDiv.style.display = 'block'; resultDiv.innerHTML = '⚠ Please enter a valid number of bathrooms (1–10).'; return; } if (isNaN(usage) || usage 200) { resultDiv.style.display = 'block'; resultDiv.innerHTML = '⚠ Daily usage per person must be between 10 and 200 gallons.'; return; } if (isNaN(pressure) || pressure 120) { resultDiv.style.display = 'block'; resultDiv.innerHTML = '⚠ Water pressure must be between 20 and 120 PSI.'; return; } if (isNaN(hardness) || hardness 100) { resultDiv.style.display = 'block'; resultDiv.innerHTML = '⚠ Water hardness must be between 0 and 100 GPG.'; return; }
// ── Step 1: Daily Water Demand (GPD) ────────────────────────────────────── // Total_GPD = Occupants × Usage_per_person var totalGPD = occupants * usage;
// ── Step 2: Peak Flow Rate (GPM) ───────────────────────────────────────── // Peak demand assumes simultaneous fixture use. // Fixtures per bathroom ≈ 3 (shower 2.0 GPM, toilet 1.6 GPM, sink 1.5 GPM) // Peak_GPM = Bathrooms × 3 fixtures × avg_fixture_flow (2.0 GPM conservative) // Capped by pipe capacity: Q = 0.4085 × P^0.5 × d^2.63 (Hazen-Williams simplified) // This calculator uses a practical rule: 1" pipe @ 60 PSI ≈ 8–10 GPM var fixtureFlowGPM = 2.0; // conservative average fixture flow var simultaneousFactor = 0.6; // not all fixtures run at once var peakFlowGPM = bathrooms * 3 * fixtureFlowGPM * simultaneousFactor;
// Pipe capacity limit (Hazen-Williams approximation for C=150 PVC): // Q_max (GPM) = 0.4085 × (pressure_loss_psi/100ft)^0.54 × d_inches^2.63 // Simplified practical limit per pipe size at given pressure: var pipeCapacity = 0.4085 * Math.pow(pressure / 100, 0.54) * Math.pow(pipeDia, 2.63) * 7.48; peakFlowGPM = Math.min(peakFlowGPM, pipeCapacity); peakFlowGPM = Math.max(peakFlowGPM, 4); // minimum 4 GPM for any home
// ── Step 3: Required Filter Flow Rate (GPM) ────────────────────────────── // Apply sediment load factor (higher sediment = need higher-rated filter) var requiredFlowGPM = peakFlowGPM * sediment;
// ── Step 4: Filter Capacity (Gallons between replacements) ─────────────── // Standard filter life = 3–6 months; use 90 days as baseline // Capacity_gal = Total_GPD × 90 days × hardness_factor // Hardness factor: harder water clogs media faster var hardnessFactor = 1 + (hardness / 50); // 1.0 at 0 GPG → 3.0 at 100 GPG var filterCapacityGal = totalGPD * 90 / hardnessFactor;
// ── Step 5: Tank / Housing Size ────────────────────────────────────────── // Standard sizes: 10"×54", 12"×52", 13"×54" tanks // Flow rate capacity by tank diameter (industry standard): // 8" → up to 7 GPM // 10" → up to 10 GPM // 12" → up to 12 GPM // 13" → up to 15 GPM var tankSize, tankFlow, housingSize; if (requiredFlowGPM 11 || sediment >= 1.5) { micronRating = '5 micron (sediment pre-filter) + 1 micron (carbon block)'; } else if (hardness > 7 || sediment >= 1.25) { micronRating = '10 micron (sediment) + 5 micron (carbon block)'; } else { micronRating = '20 micron (sediment) + 10 micron (carbon block)'; }
// ── Step 7: Pressure Drop Estimate ─────────────────────────────────────── // Typical filter pressure drop: 5–15 PSI at rated flow var pressureDrop = 5 + (requiredFlowGPM / tankFlow) * 10; var outletPressure = pressure - pressureDrop;
// ── Step 8: Annual Filter Cost Estimate ────────────────────────────────── // Replacements per year = 365 / (filterCapacityGal / totalGPD) var daysPerFilter = filterCapacityGal / totalGPD; var replacementsPerYear = 365 / daysPerFilter; var costPerFilter = housingSize.includes('dual') ? 60 : 30; // USD estimate var annualCost = replacementsPerYear * costPerFilter;
// ── Hardness Classification ─────────────────────────────────────────────── var hardnessClass; if (hardness ' + 'ParameterValue' + 'Total Daily Water Demand' + totalGPD.toFixed(0) + ' GPD' + 'Peak Flow Rate Required' + peakFlowGPM.toFixed(1) + ' GPM' + 'Design Flow Rate (with sediment factor)' + requiredFlowGPM.toFixed(1) + ' GPM' + 'Recommended Tank Size' + tankSize + '' + 'Recommended Housing' + housingSize + '' + 'Recommended Micron Rating' + micronRating + '' + 'Filter Capacity (between changes)' + filterCapacityGal.toFixed(0) + ' gallons (~' + daysPerFilter.toFixed(0) + ' days)' + 'Estimated Filter Changes / Year' + replacementsPerYear.toFixed(1) + '' + 'Estimated Annual Filter Cost$' + annualCost.toFixed(0) + '' + 'Estimated Pressure Drop' + pressureDrop.toFixed(1) + ' PSI' + 'Estimated Outlet Pressure' + outletPressure.toFixed(1) + ' PSI' + 'Water Hardness Classification' + hardnessClass + '' + '' + (outletPressure 11 ? '⚠ Very hard water detected. Consider adding a water softener upstream of the filtration system.
' : ''); }
#### Formulas Used
1. Total Daily Demand (GPD): GPD = Occupants × Daily Usage per Person
2. Peak Flow Rate (GPM): Peak GPM = Bathrooms × 3 fixtures × 2.0 GPM × 0.6 (simultaneity factor) Capped by pipe capacity: Q = 0.4085 × (P/100)^0.54 × d^2.63 × 7.48
3. Design Flow Rate: Design GPM = Peak GPM × Sediment Factor (1.0–1.5)
4. Filter Capacity (gallons between changes): Capacity = GPD × 90 days ÷ Hardness Factor Hardness Factor = 1 + (GPG ÷ 50)
5. Pressure Drop: ΔP ≈ 5 + (Design GPM ÷ Tank Rated GPM) × 10 PSI
6. Annual Filter Cost: Replacements/Year = 365 ÷ (Capacity ÷ GPD) Annual Cost = Replacements/Year × Cost per Filter
#### Assumptions & References
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