Well Recovery Rate Calculator
2 inches (0.163 gal/ft)
4 inches (0.653 gal/ft)
5 inches (1.02 gal/ft)
6 inches (1.47 gal/ft)
8 inches (2.61 gal/ft)
10 inches (4.08 gal/ft)
12 inches (5.88 gal/ft)
Select the diameter of your well casing.
Vertical distance the water rose during the test.
Duration it took for the water to rise.
Used to estimate total storage capacity.
Understanding Well Recovery Rates
For homeowners relying on private wells, understanding the recovery rate is far more critical than simply knowing the total depth of the well. The recovery rate determines the long-term sustainability of your water supply and dictates how many water-demanding appliances you can run simultaneously.
Definition: The well recovery rate is the speed at which groundwater enters the well casing to replace water that has been pumped out. It is typically measured in Gallons Per Minute (GPM).
How the Well Recovery Calculation Works
This calculator uses the volumetric capacity of your well casing to determine flow. The logic is based on physical geometry:
- Volume per Foot: Based on the diameter of the casing, we calculate how many gallons of water exist in one vertical foot of the well. A standard 6-inch casing holds approximately 1.47 gallons per foot.
- Total Volume Recovered: By measuring how many feet the water level rises after the pump is turned off, we calculate the total volume of water that entered the well.
- Flow Rate: Dividing the total volume by the time it took to rise gives us the flow rate (GPM).
Standard Well Casing Volumes
| Casing Diameter (Inches) | Volume (Gallons per Foot) |
|---|---|
| 4″ | 0.653 |
| 6″ | 1.469 |
| 8″ | 2.611 |
Interpreting Your Results
Is your well recovery rate sufficient? Here are the general industry guidelines for a standard single-family home:
- Less than 1 GPM: Considered a low-yield well. You will likely need additional storage tanks or a cistern system to buffer peak usage times (like morning showers).
- 1 to 5 GPM: Marginal to Average. Careful water management is required. Avoid running the dishwasher, washing machine, and sprinklers simultaneously.
- 5 to 10 GPM: Good. Sufficient for most modern households with standard appliances.
- 10+ GPM: Excellent. Capable of supporting irrigation systems and high-demand usage.
How to Perform a Recovery Test
To get accurate numbers for the inputs above, follow these steps safely (consult a professional if unsure):
- Run water until the pump kicks on and the water level drops (drawdown).
- Turn off the pump/water usage immediately.
- Measure the depth to the water (Static Level 1).
- Wait a specific amount of time (e.g., 15 minutes).
- Measure the depth to the water again (Static Level 2).
- The difference between Level 1 and Level 2 is your Water Level Rise input.
Results
'; outputHtml += 'Well Recovery Rate:
';
outputHtml += '' + gpm.toFixed(2) + ' GPM
';
outputHtml += " + statusText + ";
outputHtml += '';
outputHtml += '
';
// Optional: Storage capacity if depth is provided
if (!isNaN(parseFloat(depthStr)) && parseFloat(depthStr) > 0) {
var depth = parseFloat(depthStr);
var totalStorage = depth * gallonsPerFoot;
outputHtml += 'Hourly Rate:' + gph.toFixed(0) + ' gal/hr
';
outputHtml += 'Daily Potential:' + gpd.toFixed(0) + ' gal/day
';
outputHtml += 'Volume Recovered:' + totalGallonsRecovered.toFixed(1) + ' gallons
';
outputHtml += 'Casing Volume:' + gallonsPerFoot.toFixed(3) + ' gal/ft
';
outputHtml += '';
outputHtml += 'Total Static Borehole Storage: ' + totalStorage.toFixed(0) + ' Gallons (Full Column)';
outputHtml += '
';
}
var resultArea = document.getElementById('result-area');
resultArea.innerHTML = outputHtml;
resultArea.style.display = 'block';
resultArea.className = (gpm < 1) ? 'result-warning' : 'result-success';
}