How to Test Your Soil Drainage
Test soil drainage by filling a 12-inch-deep hole with water, letting it drain once, then refilling it and measuring the second drop in water level over an hour. A rate of roughly 1 to 2 inches per hour suits many garden plants, while much slower drainage signals a site that may need a different crop, raised bed, or drainage solution.
Choose a representative spot in the planting area, avoiding obvious low places, recently filled holes, and areas directly beside downspouts. If the garden has visibly different soil zones, test each zone separately. Do the test when the soil is moist but not frozen, saturated from a recent storm, or extremely dry. Testing several days after rain often gives a more useful picture of normal conditions.
Dig a hole about 12 inches deep and 8 to 12 inches wide with vertical sides. Remove loose soil from the bottom without compacting it, and avoid smearing the sides in wet clay. Fill the hole completely with water and let it drain away. This first filling pre-wets the surrounding soil, making the measured second filling more representative.
Refill the hole to the same level after the first water has drained. Measure the water depth immediately, then measure again after one hour. The difference is the drainage rate in inches per hour. For a more detailed result, record the water level every 15 minutes, especially if it drains quickly or very slowly.
Many vegetable beds perform well when the second filling drains about 1 to 2 inches per hour. Less than 1 inch per hour suggests slow drainage, which can keep roots in overly wet soil after rain. More than about 3 inches per hour suggests very rapid drainage, often associated with sandy soil that may need more compost, mulch, and careful irrigation. These figures are useful guidelines, not a substitute for observing the site through wet seasons.
If water remains in the hole after several hours or drains very little overnight, investigate before planting moisture-sensitive crops. Check whether the site is a natural low point, whether runoff collects there, or whether a compacted layer lies beneath the topsoil. Dig a small inspection hole nearby to look for dense, layered, or gray mottled soil. Local Cooperative Extension staff can help interpret persistent drainage issues and regional soil conditions.
Improve a slow-draining garden area with the least disruptive option that fits the cause. For a small vegetable plot, raised beds filled with a well-blended growing medium can lift roots above saturated ground. Add finished compost over time, keep traffic off wet beds to prevent compaction, and redirect surface runoff where appropriate and permitted. Do not install drains or alter grading near buildings, property lines, or waterways without understanding local requirements and the full water path.
Frequently asked questions
Why fill the drainage test hole twice?
The first filling wets the sides and surrounding soil. Measuring the second filling reduces the effect of unusually dry soil and gives a more representative drainage rate.
Can I test drainage right after heavy rain?
Wait until the soil is no longer saturated. A test immediately after heavy rain can make normal soil appear slower draining than it usually is.
What should I plant in a slow-draining bed?
Use raised beds for many vegetables, or select plants adapted to moist conditions based on local guidance. Avoid forcing drought-adapted crops into a spot that stays wet after rain.
General guidance for US home gardens. Conditions vary by region and season; check with your local Cooperative Extension office for site-specific advice. Page updated Aug 4, 2026.