Total distance the water rose in the well during the test.
How long it took for the water to rise the distance entered above.
0.00 GPM
Gallons Recovered:0.00 gal
Potential Daily Yield:0 gal/day
Volume per Foot of Casing:0.00 gal/ft
Understanding Well Recovery Rates
The Well Recovery Rate determines how quickly an aquifer replenishes the water in your well casing after it has been pumped or bailed. Unlike a static water level, the recovery rate measures the active flow capability of your well, which is critical for sizing pumps and ensuring a consistent household water supply.
How It Is Calculated
This calculator determines the recovery rate using the volumetric capacity of the well casing. By measuring how many feet the water level rises over a specific period, we calculate the volume of water replenished and divide it by the time elapsed.
The formula for the volume of water in a cylindrical casing is:
Volume (gallons) = π × r² × h × 7.48
r = Radius of the casing in feet
h = Height of water rise in feet
7.48 = Gallons per cubic foot of water
Interpreting Your Results (GPM)
The standard metric for well yield is Gallons Per Minute (GPM).
< 1 GPM (Low Yield): Often insufficient for modern households without an intermediate storage tank or cistern system. Requires careful water management.
1 – 5 GPM (Moderate Yield): Generally acceptable for smaller households. A larger pressure tank is recommended to buffer peak usage times (like showers and laundry).
5+ GPM (Good Yield): Considered the standard for a typical single-family home. This rate allows for simultaneous appliance usage without running the well dry.
Pro Tip: If your recovery rate is low, do not oversize your well pump. Installing a pump that draws water faster than the well recovers can cause pump burnout and introduce sediment into your plumbing.
Factors Affecting Recovery
Several geological and mechanical factors influence how fast your well recovers:
Aquifer Permeability: Sand and gravel aquifers usually recover faster than solid bedrock or clay-heavy formations.
Well Depth: Deeper wells often have a larger storage column, which can compensate for a slower recovery rate.
Well Screen Condition: Over time, mineral deposits or bio-fouling can clog the well screen, significantly reducing the recovery rate.
Seasonal Changes: Water tables fluctuate with rainfall and drought, often reducing recovery rates in late summer.
function calculateRecovery() {
// 1. Get input values
var diameterStr = document.getElementById("casingDiameter").value;
var riseStr = document.getElementById("waterRise").value;
var timeStr = document.getElementById("timeElapsed").value;
// 2. Parse values
var diameter = parseFloat(diameterStr);
var rise = parseFloat(riseStr);
var time = parseFloat(timeStr);
// 3. Validation
if (isNaN(diameter) || isNaN(rise) || isNaN(time) || time <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
// 4. Logic Calculation
// Convert diameter (inches) to radius (feet)
// Radius in inches = diameter / 2
// Radius in feet = (diameter / 2) / 12
var radiusFt = (diameter / 2.0) / 12.0;
// Calculate Volume in Cubic Feet: PI * r^2 * h
var volumeCubicFt = Math.PI * Math.pow(radiusFt, 2) * rise;
// Convert Cubic Feet to Gallons (1 cubic foot = 7.48052 gallons)
var volumeGallons = volumeCubicFt * 7.48052;
// Calculate Gallons Per Minute (GPM)
var gpm = volumeGallons / time;
// Calculate Gallons Per Day (GPD)
var gpd = gpm * 60 * 24;
// Calculate Volume Per Foot (for reference)
var volPerFootCubic = Math.PI * Math.pow(radiusFt, 2) * 1;
var volPerFootGal = volPerFootCubic * 7.48052;
// 5. Display Results
document.getElementById("wrrResult").style.display = "block";
document.getElementById("gpmResult").innerHTML = gpm.toFixed(2) + " GPM";
document.getElementById("volResult").innerHTML = volumeGallons.toFixed(1) + " gal";
document.getElementById("gpdResult").innerHTML = Math.round(gpd).toLocaleString() + " gal/day";
document.getElementById("volPerFootResult").innerHTML = volPerFootGal.toFixed(2) + " gal/ft";
// 6. Status Logic
var statusBox = document.getElementById("statusBox");
statusBox.className = "wrr-status-box"; // reset classes
if (gpm < 1) {
statusBox.innerHTML = "Status: Low Yield (Requires Storage System)";
statusBox.classList.add("status-low");
} else if (gpm < 5) {
statusBox.innerHTML = "Status: Moderate Yield (Adequate for Basic Needs)";
statusBox.classList.add("status-medium");
} else {
statusBox.innerHTML = "Status: Good Yield (Standard Residential)";
statusBox.classList.add("status-good");
}
}