function calculatePercolation() {
// Get inputs by ID
var waterInput = document.getElementById("waterAmount");
var timeInput = document.getElementById("percolationTime");
var resultContainer = document.getElementById("perc-result-container");
var resultValue = document.getElementById("resultValue");
var resultInterp = document.getElementById("resultInterpretation");
var waterError = document.getElementById("waterError");
var timeError = document.getElementById("timeError");
// Reset errors
waterError.style.display = "none";
timeError.style.display = "none";
resultContainer.style.display = "none";
// Parse values
var volume = parseFloat(waterInput.value);
var time = parseFloat(timeInput.value);
// Validation
var hasError = false;
if (isNaN(volume) || volume <= 0) {
waterError.style.display = "block";
hasError = true;
}
if (isNaN(time) || time 300) {
soilType = "Very Sandy / Gravelly";
description = "Water drains extremely fast. This soil may have difficulty retaining moisture and nutrients for plant growth.";
} else if (rate > 100) {
soilType = "Sandy Soil";
description = "Fast drainage. Good for drought-tolerant plants, but requires frequent watering.";
} else if (rate >= 10 && rate <= 100) {
soilType = "Loamy Soil / Moderate";
description = "Ideal drainage for most agricultural and gardening purposes. Retains enough moisture while preventing waterlogging.";
} else if (rate < 10) {
soilType = "Clay / Silt";
description = "Slow drainage. High risk of waterlogging, which can cause root rot. Soil compaction may be an issue.";
}
// Update DOM
resultValue.innerHTML = rate.toFixed(2) + " mL/min";
resultInterp.innerHTML = "Estimated Soil Type: " + soilType + "" + description;
// Show Result
resultContainer.style.display = "block";
}
How to Calculate Percolation Rate: A Complete Guide
Understanding soil percolation rate is essential for agriculture, gardening, construction, and environmental engineering. It measures how quickly water moves through soil, which directly impacts irrigation planning, septic tank installation, and plant health.
What is Percolation Rate?
Percolation rate is the speed at which water flows through the soil pores. It is usually expressed in milliliters per minute (mL/min) for laboratory or small-scale field tests, or in inches/hour (or minutes/inch) for septic system site analysis (often called a "perc test").
High percolation rates indicate sandy soil where water drains quickly, often carrying nutrients away. Low percolation rates indicate clay-heavy or compacted soil, which can lead to waterlogging and root diseases.
The Percolation Rate Formula
The calculation is straightforward. It is the ratio of the volume of water infiltrated to the time taken for that infiltration to occur.
Percolation Rate (mL/min) = Amount of Water (mL) / Time Taken (min)
Example Calculation:
You pour 500 mL of water into your soil test hole.
It takes exactly 25 minutes for the water to completely drain away.
Calculation: 500 / 25 = 20 mL/min.
How to Perform a Simple Soil Percolation Test
To use the calculator above effectively, you can perform a simple "jar test" or "hole test" in your garden:
Dig a hole: Dig a hole about 30cm deep and 30cm wide.
Pre-soak: Fill the hole with water and let it drain completely. This saturates the soil to give a more accurate reading (dry soil absorbs water artificially fast).
Measure Water: Measure a specific amount of water (e.g., 1000 mL) using a measuring jug.
Pour and Time: Pour the water into the hole and immediately start a stopwatch.
Stop: Stop the timer the moment the standing water disappears from the bottom of the hole.
Calculate: Input your volume (mL) and time (minutes) into the calculator above.
Interpreting Your Results
Knowing your rate helps you amend your soil effectively:
Fast (High Rate): Usually sandy soil. Add organic matter like compost or peat moss to improve water retention.
Moderate (Medium Rate): Often loamy soil. This is the "Goldilocks" zone for most plants.
Slow (Low Rate): Usually clay or compacted soil. Aeration and adding organic matter or gypsum can help break up the clay structure and improve drainage.
Why is this important for Septic Systems?
For construction, specifically septic leach fields, a "Perc Test" determines if the ground can absorb the wastewater effluent. If the rate is too slow, the system may back up. If it is too fast, the wastewater may reach the groundwater table before it is properly treated by the soil bacteria.