The pool water turnover rate is the amount of time it takes for your filtration system to cycle the entire volume of your pool's water through the filter exactly once. This is a critical metric for maintaining water clarity and hygiene.
The Turnover Formula
To calculate the turnover rate, we use two primary steps:
Volume Calculation: Length × Width × Average Depth × 7.48 (gallons per cubic foot).
Turnover Rate: Total Gallons ÷ (Flow Rate in GPM × 60 minutes).
Why Does Turnover Matter?
If your turnover rate is too slow, contaminants like algae, bacteria, and debris stay in the water longer than they should. A standard residential pool should ideally achieve a full turnover every 6 to 8 hours. Commercial pools, which face higher bather loads, usually require a turnover every 4 to 6 hours.
Practical Example:
A 16′ x 32′ pool with an average depth of 5′ holds approximately 19,148 gallons. If your pump operates at 40 GPM, the calculation would be: 19,148 / (40 x 60) = 7.97 hours. This pool meets the standard residential requirement.
Recommended Turnover Guidelines
Pool Type
Target Turnover
Residential Pool
6 – 8 Hours
Public/Commercial Pool
4 – 6 Hours
Spas & Hot Tubs
20 – 30 Minutes
Wading Pools
1 – 2 Hours
function calculateTurnover() {
var length = parseFloat(document.getElementById('pool_length').value);
var width = parseFloat(document.getElementById('pool_width').value);
var depth = parseFloat(document.getElementById('pool_depth').value);
var gpm = parseFloat(document.getElementById('flow_rate').value);
if (isNaN(length) || isNaN(width) || isNaN(depth) || isNaN(gpm) || length <= 0 || width <= 0 || depth <= 0 || gpm <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
// Calculate Volume (Rectangular)
// Cubic Feet * 7.48 = Gallons
var volume = length * width * depth * 7.48;
// Calculate Turnover Rate in Hours
// Volume / (Gallons Per Hour)
var gph = gpm * 60;
var turnoverHours = volume / gph;
// Turnovers per 24 hours
var turnoversPerDay = 24 / turnoverHours;
// Display Results
document.getElementById('res_volume').innerText = Math.round(volume).toLocaleString();
document.getElementById('res_turnover').innerText = turnoverHours.toFixed(2);
document.getElementById('res_perday').innerText = turnoversPerDay.toFixed(2);
var statusText = "";
var statusColor = "";
if (turnoverHours <= 8) {
statusText = "Excellent (Ideal for Residential)";
statusColor = "#28a745";
} else if (turnoverHours <= 10) {
statusText = "Acceptable (Run pump longer)";
statusColor = "#ffc107";
} else {
statusText = "Poor (Risk of stagnant water)";
statusColor = "#dc3545";
}
var statusEl = document.getElementById('res_status');
statusEl.innerText = statusText;
statusEl.style.color = statusColor;
statusEl.style.fontWeight = "bold";
document.getElementById('results_area').style.display = 'block';
}