Chicago Water Pressure Calculator

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Chicago Water Pressure Calculator

Calculate water pressure at a given location in Chicago's water distribution system based on elevation, floor level, and system supply pressure.

Water Main Supply Pressure (psi)

Typical Chicago street-level main pressure: 60–100 psi

Street Elevation at Your Location (ft above sea level)

Chicago elevations range ~578–672 ft. Average street level ≈ 595 ft

Floor Number

Ground floor = 1. Each floor adds ~10 ft of elevation.

Floor-to-Floor Height (ft)

Residential: ~9–10 ft; Commercial: ~12–14 ft

Estimated Pipe Friction Loss (psi)

Typical residential service line loss: 2–10 psi

Calculate Pressure

function chiCalc() { var supplyPsi = parseFloat(document.getElementById('chi-supply-pressure').value); var streetElev = parseFloat(document.getElementById('chi-street-elevation').value); var floor = parseFloat(document.getElementById('chi-floor').value); var floorHeight = parseFloat(document.getElementById('chi-floor-height').value); var pipeLoss = parseFloat(document.getElementById('chi-pipe-loss').value); var resultDiv = document.getElementById('chi-result');

// --- Validation --- if (isNaN(supplyPsi) || isNaN(streetElev) || isNaN(floor) || isNaN(floorHeight) || isNaN(pipeLoss)) { resultDiv.innerHTML = 'Please fill in all fields with valid numbers.'; return; } if (supplyPsi 200) { resultDiv.innerHTML = 'Supply pressure must be between 1 and 200 psi.'; return; } if (streetElev 680) { resultDiv.innerHTML = 'Street elevation must be between 570 and 680 ft (Chicago range).'; return; } if (floor 200) { resultDiv.innerHTML = 'Floor number must be between 1 and 200.'; return; } if (floorHeight 20) { resultDiv.innerHTML = 'Floor-to-floor height must be between 8 and 20 ft.'; return; } if (pipeLoss 50) { resultDiv.innerHTML = 'Pipe friction loss must be between 0 and 50 psi.'; return; }

// --- Core Formula --- // Elevation of the fixture above street level // Floor 1 = ground level (0 ft above street); Floor 2 = 1 * floorHeight, etc. var floorsAboveGround = floor - 1; var fixtureElevAboveStreet = floorsAboveGround * floorHeight; // ft

// Pressure loss due to elevation: 1 psi = 2.31 ft of water head // ΔP_elevation = h / 2.31 var elevationPressureLoss = fixtureElevAboveStreet / 2.31; // psi

// Residual pressure at fixture // P_fixture = P_supply - ΔP_elevation - P_friction var fixturePressure = supplyPsi - elevationPressureLoss - pipeLoss;

// Chicago Water Dept minimum service pressure: 20 psi at meter var minCode = 20; var status, statusColor; if (fixturePressure >= 60) { status = "Excellent – well within Chicago Water Dept. standards."; statusColor = "#27ae60"; } else if (fixturePressure >= 40) { status = "Good – adequate for normal residential/commercial use."; statusColor = "#2980b9"; } else if (fixturePressure >= minCode) { status = "Marginal – meets minimum code but may feel low at fixtures."; statusColor = "#e67e22"; } else { status = "Insufficient – below Chicago minimum 20 psi. Booster pump likely required."; statusColor = "#c0392b"; }

// Pressure head equivalent var pressureHead = fixturePressure * 2.31; // ft of water

var html = '### Results '; html += ''; html += 'Supply Pressure at Main' + supplyPsi.toFixed(1) + ' psi'; html += 'Fixture Height Above Street' + fixtureElevAboveStreet.toFixed(1) + ' ft'; html += 'Elevation Pressure Loss' + elevationPressureLoss.toFixed(2) + ' psi'; html += 'Pipe Friction Loss' + pipeLoss.toFixed(1) + ' psi'; html += 'Estimated Fixture Pressure' + fixturePressure.toFixed(1) + ' psi (' + pressureHead.toFixed(0) + ' ft head)'; html += ''; html += 'Status: ' + status + '

';

if (fixturePressure 80) { html += 'Note: Pressure exceeds 80 psi. Chicago code recommends a pressure-reducing valve (PRV) to protect fixtures and reduce water hammer.

'; }

resultDiv.innerHTML = html; }

#### Formula

Pfixture = Psupply − (h / 2.31) − Pfriction

Example: 80 psi supply, 5th floor (40 ft above street), 5 psi friction loss: P = 80 − (40 / 2.31) − 5 = 80 − 17.32 − 5 = 57.68 psi

#### Assumptions & References

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References

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