Standard turnover is 8 to 10 hours for residential pools.
Required Flow Rate (GPM):–
Flow Rate (Gallons Per Hour):–
Understanding Pool Flow Rate and Turnover
Calculating the correct flow rate is essential for maintaining crystal clear, safe water in your swimming pool. The flow rate determines how quickly water moves through your filtration system to remove debris, bacteria, and algae.
What is Turnover Rate?
The "Turnover Rate" is the amount of time it takes for the entire volume of water in your pool to pass through the filter and pump system exactly once. Most health codes and pool professionals recommend a turnover rate between 8 and 10 hours for residential pools, and often 6 hours or less for commercial pools.
How to Calculate Flow Rate (GPM)
Flow rate is typically measured in Gallons Per Minute (GPM). To find your required GPM, you need two numbers: your pool's total volume and your target turnover time.
Divide volume by minutes: 20,000 ÷ 480 = 41.67 GPM.
Choosing the Right Pump Size
Once you know your required flow rate (e.g., 42 GPM), you can select a pool pump. However, bigger isn't always better. You need a pump that can handle the required flow rate against the "Total Dynamic Head" (resistance) of your plumbing, but you also need to ensure your pipes and filter can handle that pressure.
Pipe Sizing Guidelines
Pushing water too fast through small pipes creates excessive noise and puts strain on the pump. General guidelines for maximum flow rates in PVC piping are:
1.5-inch Pipe: Max recommended flow ~40-50 GPM
2.0-inch Pipe: Max recommended flow ~70-80 GPM
2.5-inch Pipe: Max recommended flow ~110-120 GPM
Using the calculator above will help you verify if your current plumbing setup is adequate for the turnover rate you desire.
function calculatePoolFlow() {
// 1. Get input values
var volumeInput = document.getElementById('poolVolume');
var timeInput = document.getElementById('turnoverTime');
var volume = parseFloat(volumeInput.value);
var hours = parseFloat(timeInput.value);
// 2. Validate inputs
if (isNaN(volume) || volume <= 0) {
alert("Please enter a valid pool volume greater than 0.");
return;
}
if (isNaN(hours) || hours <= 0) {
alert("Please enter a valid turnover time greater than 0.");
return;
}
// 3. Perform Calculations
// Formula: GPM = Volume / (Hours * 60)
var totalMinutes = hours * 60;
var gpm = volume / totalMinutes;
var gph = volume / hours;
// 4. Generate Recommendation based on standard PVC pipe velocity caps (approx 6-8 ft/sec)
var recommendation = "";
if (gpm <= 44) {
recommendation = "Plumbing Tip: A flow rate of " + gpm.toFixed(1) + " GPM can typically be handled by 1.5-inch piping or larger.";
} else if (gpm <= 75) {
recommendation = "Plumbing Tip: For " + gpm.toFixed(1) + " GPM, you should have at least 2-inch piping to avoid high pressure.";
} else if (gpm <= 120) {
recommendation = "Plumbing Tip: High flow! You need at least 2.5-inch piping for this system.";
} else {
recommendation = "Plumbing Tip: Very high flow rate. Requires 3-inch+ commercial piping or multiple pumps.";
}
// 5. Update HTML Output
document.getElementById('resGPM').innerHTML = gpm.toFixed(2) + " GPM";
document.getElementById('resGPH').innerHTML = Math.round(gph).toLocaleString() + " Gal/Hr";
document.getElementById('pipeRec').innerHTML = recommendation;
// 6. Show results container
document.getElementById('resultsOutput').style.display = "block";
}