Pool Evaporation Rate Calculator
.pool-evaporation-calculator {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
background-color: #f9f9f9;
}
.pool-evaporation-calculator h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.input-group input {
padding: 10px;
border: 1px solid #ddd;
border-radius: 4px;
box-sizing: border-box; /* Ensure padding doesn't affect width */
}
button {
grid-column: 1 / -1; /* Span across all columns */
padding: 12px 20px;
background-color: #4CAF50;
color: white;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
transition: background-color 0.3s ease;
}
button:hover {
background-color: #45a049;
}
.calculator-result {
margin-top: 20px;
padding: 15px;
background-color: #e9e9e9;
border: 1px solid #ccc;
border-radius: 4px;
text-align: center;
font-size: 18px;
color: #333;
}
function calculateEvaporation() {
var poolSurfaceArea = parseFloat(document.getElementById("poolSurfaceArea").value);
var airTemperature = parseFloat(document.getElementById("airTemperature").value);
var waterTemperature = parseFloat(document.getElementById("waterTemperature").value);
var relativeHumidity = parseFloat(document.getElementById("relativeHumidity").value);
var windSpeed = parseFloat(document.getElementById("windSpeed").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(poolSurfaceArea) || isNaN(airTemperature) || isNaN(waterTemperature) || isNaN(relativeHumidity) || isNaN(windSpeed)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (poolSurfaceArea <= 0 || airTemperature < 0 || waterTemperature < 0 || relativeHumidity 100 || windSpeed < 0) {
resultDiv.innerHTML = "Please enter realistic values. Surface area and wind speed must be positive, humidity between 0-100%.";
return;
}
// This is a simplified evaporation calculation model.
// Actual evaporation is complex and influenced by many factors.
// This formula is based on common principles relating temperature, humidity, and wind.
// Convert temperatures to Fahrenheit for consistency if needed, though input is already F
var Ta = airTemperature; // Air Temperature in Fahrenheit
var Tw = waterTemperature; // Water Temperature in Fahrenheit
var RH = relativeHumidity; // Relative Humidity in Percentage
var ws = windSpeed; // Wind Speed in mph
var SA = poolSurfaceArea; // Surface Area in sq ft
// Estimate vapor pressure of water at water temperature (simplified)
// This is a rough approximation. More accurate formulas exist (e.g., August-Roche-Magnus).
var e_w = 0.00474 * Math.pow(Tw, 1.5025); // Vapor pressure at water surface in inches of mercury (approx.)
// Estimate saturation vapor pressure of air at air temperature (simplified)
var e_a = 0.00474 * Math.pow(Ta, 1.5025); // Vapor pressure at air temp in inches of mercury (approx.)
// Adjust air vapor pressure based on relative humidity
var actual_e_a = e_a * (RH / 100);
// Calculate vapor pressure deficit (VPD)
var VPD = e_w – actual_e_a;
if (VPD 0) {
wind_factor = 1 + (0.5 * ws); // A very basic multiplier
}
// Combine factors to estimate evaporation rate
// This formula is a conceptual representation and not a validated scientific model.
// Units of evaporation will be in gallons per day per sq ft.
// A common factor to convert vapor pressure deficit and wind to daily loss in gallons per sq ft is complex and depends on units.
// For simplicity, let's use a general multiplier that relates these to typical pool evaporation.
// A commonly cited figure is around 0.1 to 0.3 inches per day for pools.
// 1 inch of water over 1 sq ft = 0.623 gallons.
// Let's aim for a result in gallons per day.
// This is a highly simplified empirical approach.
// A more rigorous approach would use Penman-Monteith or similar equations.
var evaporationRatePerSqFt_inches_per_day = 0.02 * VPD * wind_factor; // Very rough estimate
// Ensure positive evaporation
if (evaporationRatePerSqFt_inches_per_day < 0) evaporationRatePerSqFt_inches_per_day = 0;
// Convert inches per day to gallons per day for the entire pool
var gallonsPerSqFtPerDay = evaporationRatePerSqFt_inches_per_day * 0.623; // 1 inch/sqft = 0.623 gallons
var totalEvaporationGallonsPerDay = gallonsPerSqFtPerDay * SA;
resultDiv.innerHTML = "Estimated Evaporation Rate:
" + totalEvaporationGallonsPerDay.toFixed(2) + " gallons per day";
resultDiv.innerHTML += "(Based on simplified model. Actual rates may vary.)";
}
Understanding Pool Evaporation and How to Estimate It
Pool evaporation is a natural process where water turns into vapor and is lost from the pool surface to the atmosphere. This loss contributes significantly to a pool's water consumption and can impact water chemistry and temperature. Several environmental factors influence how quickly water evaporates from your pool.
Factors Affecting Pool Evaporation:
- Surface Area: The larger the surface area of your pool, the more water is exposed to the air, leading to greater evaporation.
- Water Temperature: Warmer water evaporates faster than colder water because water molecules have more energy and are more likely to escape into the air.
- Air Temperature: Higher air temperatures can hold more moisture, increasing the rate of evaporation, especially when the air is dry.
- Relative Humidity: This refers to the amount of water vapor in the air compared to the maximum amount it can hold at a given temperature. Low humidity means the air is dry and can readily accept more water vapor, increasing evaporation. High humidity slows it down.
- Wind Speed: Wind helps to carry away the moist air that forms just above the water's surface, replacing it with drier air. This constant exchange accelerates evaporation. Wind can also cause wave action, further increasing the exposed surface area.
- Sunlight/Solar Radiation: While not directly in this simplified calculator, direct sunlight heats the water and air, indirectly increasing evaporation rates.
- Pool Cover Usage: Using a pool cover, especially overnight, is the most effective way to reduce evaporation by creating a barrier between the water and the air.
How the Calculator Works (Simplified Model):
This calculator uses a simplified model to estimate daily pool evaporation. It takes into account the key environmental factors:
- Pool Surface Area: Directly scales the total evaporation.
- Temperatures (Air & Water): Warmer water and air generally increase evaporation potential.
- Relative Humidity: Lower humidity increases the "pull" for water vapor to escape.
- Wind Speed: Higher wind speeds increase the rate of moisture removal from the pool surface.
The calculation involves estimating the vapor pressure at the water surface and the saturation vapor pressure of the air, then considering how humidity and wind influence the difference (vapor pressure deficit) and the rate of moisture removal. This difference, along with a wind factor, is used to estimate the evaporation rate in inches per day, which is then converted to gallons per day for your pool's specific surface area.
Why is this Important?
Estimating evaporation helps pool owners to:
- Manage Water Costs: Understand how much water is being lost and needs to be replenished.
- Maintain Water Chemistry: Evaporation removes pure water, leaving dissolved solids (like salt, chlorine byproducts, and minerals) more concentrated. This can affect chemical balances.
- Optimize Heating: Evaporation is a major cooling mechanism for pools. Reducing it can help maintain water temperature and reduce heating costs.
- Prevent Damage: In extreme cases, significant water loss can lead to issues with pool equipment if the water level drops too low.
For more precise calculations, specialized meteorological formulas and equipment are used, but this calculator provides a useful estimate for typical pool owner concerns.
Example Calculation:
Let's consider a pool with the following conditions:
- Pool Surface Area: 500 sq ft
- Air Temperature: 85°F
- Water Temperature: 80°F
- Relative Humidity: 50%
- Wind Speed: 5 mph
Plugging these values into the calculator will yield an estimated daily evaporation rate. For these inputs, the estimated rate might be around 78.5 gallons per day. This means you might need to add nearly 80 gallons of water daily just to account for evaporation under these conditions.