French Drain Gravel Calculator
Calculate French Drain Materials
Estimate gravel, pipe, and fabric for a French drain
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Formula
Gravel Tons = (Trench Volume - Pipe Volume) / 27 x 2,700 lbs/yd3 / 2,000 x 1.10
Frequently Asked Questions
What size gravel for a French drain?
Use washed 3/4-inch to 1.5-inch crushed stone or river rock. Avoid pea gravel (too small, clogs easily) and large stones (too many gaps). The gravel must allow water to flow while filtering sediment.
How deep should a French drain be?
A standard French drain should be 18-24 inches deep and 9-12 inches wide. The trench must slope at least 1 inch per 8 feet (1% grade) toward the discharge point.
Do I need landscape fabric for a French drain?
Yes, landscape fabric prevents soil and silt from clogging the gravel and pipe over time. Line the trench with fabric, add gravel and pipe, then fold the fabric over the top before backfilling.
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