Conduct a “perk” test in your yard before planting to test soil drainage.
Almost every garden instruction guide refers to the importance of “well-draining soil.” If water drains (percolates) away from plant roots too quickly, the plants will parch even if they’re getting regular water. And if water doesn’t drain, many plants will drown and rot from the roots up. A percolation test — or perk test — is a great way to measure drainage in your lawn or garden soil.
Here’s how to conduct an easy, DIY soil perc test in your yard.
What a Soil Percolation Test Tells You
A soil percolation test provides valuable insights into your yard’s drainage capabilities. It reveals how quickly water moves through your soil, indicating whether you have well-draining soil, poorly-draining soil, or something in between.
You can use this information when you select plants, determine if you need to improve drainage and avoid issues like root rot or drought stress. By understanding your soil’s percolation rate, you can make informed decisions about plant selection and soil amendments in your garden beds.
Supplies You Need For Soil Percolation Test
To perform a DIY soil drainage perk test, gather a shovel for digging, a ruler or tape measure for accurate measurements, a watch, smartphone, or timer to track drainage time, and a straight edge like a board or stick to help measure water levels.
You’ll also need a water source to fill the test hole. These simple supplies will allow you to conduct an accurate perk test without any specialized equipment.
Soil Percolation Test
Here are the steps for doing a soil percolation test.
Step 1: Dig Hole
Dig a hole at least 12” in diameter by 12” deep, with straight sides. If you’re testing your entire property, dig several holes scattered around your yard since drainage can vary.
Step 2: Fill Hole with Water
Fill the hole with water and let it sit overnight. This saturates the soil and helps give a more accurate test reading.
Step 3: Refill Hole with Water
The next day, refill the hole with water.
Step 4: Measure Water Level
Measure the water level by laying a stick, pipe, or other straight edge across the top of the hole, then use a tape measure or yardstick to determine the water level.
Step 5: Measure Drainage Every Hour
Continue to measure the water level every hour until the hole is empty, noting the number of inches the water level drops per hour.
Ideal Soil Drainage
The ideal soil drainage is around 2” per hour, with readings between 1”- 3” generally OK for garden plants that have average drainage needs. If the rate is less than 1” per hour, your drainage is too slow, and you’ll need to improve drainage or choose plants tolerant of wet soil. If drainage is more than 4” per hour, it’s too fast. Drainage problems can be addressed by:
- Incorporate plenty of compost and organic matter into the soil. Organic matter helps heavy clay soil to drain and helps coarse sandy soil to hold moisture, so it’s a win-win no matter what your soil type.
- Choose plants suited to your soil drainage.
- Build raised beds for better control over the soil texture.
If you’ve ever installed a septic system in your yard, you’re probably familiar with soil percolation tests. Professional perk tests are measured in minutes per inch (MPI). To convert your DIY drainage measurements to MPI, divide the time (in minutes) by the distance (in inches) the water level fell. For example, a rate of 2” per hour would correspond to a perk rate of 30 MPI (60 minutes ÷ 2 inches = 30 MPI).
How to Improve Your Soil Drainage
If your perk test reveals poor drainage, don’t worry — there are several ways you can improve it. Incorporating organic matter like compost into your soil can significantly enhance drainage in clay soils while improving water retention in sandy soils.
For severely compacted areas, consider aerating or tiling the soil or installing drainage solutions like French drains. Raised beds are another excellent option for controlling soil composition and drainage. Remember, gradual improvements over time can lead to significant changes in your soil’s health and drainage capacity.
Final Thoughts
Conducting a DIY soil drainage perk test for your yard is a simple yet powerful way to understand and improve your garden’s growing conditions. As someone who has helped countless homeowners transform their outdoor spaces, I can’t stress enough the importance of this fundamental step in starting a garden for your home.
Frequently Asked Questions
How often should I perform a soil drainage perk test?
I recommend performing a perk test before starting a new garden or landscape project, and repeat every 3–5 years or if you notice drainage issues.
Can I do a perk test in winter?
No, it’s best to conduct perk tests when the ground isn’t frozen, typically in spring, summer, or fall for most accurate results.
What if my soil drains too quickly?
If water drains faster than four inches per hour, add organic matter to keep water in and consider plants that can handle dry conditions.
Further Information
- Soil Drainage (Bartlett Tree Resource Laboratories)
- Organic Gardening 101 (article)
