How to Perform a Soil Percolation Test Before Choosing a Drainage Solution

Before choosing any drainage solution — whether Hydro Fix, a French drain, a drywell, or something else entirely — you need to understand how your soil handles water. A percolation test is the most reliable way to get that answer.

What Is a Percolation Test?

A percolation test (or "perc test") measures how quickly water drains through your soil. The result tells you whether your soil can absorb water fast enough to support a subsurface drainage system, and if so, how large that system needs to be.

How to Perform a Basic Percolation Test

• Dig a test hole: Approximately 12 inches wide and 12 inches deep in the problem area.
• Pre-soak the hole: Fill it with water and let it drain completely. This saturates the soil to simulate real storm conditions.
• Perform the test: Fill the hole with 6 inches of water. Start a timer.
• Measure drainage rate: Record how many minutes it takes for the water level to drop 1 inch. This is your percolation rate.

Interpreting the Results

• Under 30 min/inch: Excellent. Most drainage solutions will work well.
• 30–60 min/inch: Acceptable. System sizing will need to account for slower absorption.
• 60–120 min/inch: Challenging. Drainage systems are possible but must be carefully designed.
• Over 120 min/inch: Very poor. Standard subsurface drainage may not be sufficient without additional measures.

Why This Matters for Hydro Fix

Hydro Fix moves water efficiently to a discharge point — but that water still needs somewhere to go. If soil percolation is very poor, we may recommend pairing the Hydro Fix system with a daylight discharge, stormwater box with controlled release, or connection to an existing storm drain. The percolation test tells us exactly what's needed before we design anything.

This is why Hydro Fix always starts with a site evaluation rather than jumping straight to installation — the right design depends entirely on your specific soil and site conditions.