What a 75 ft French drain takes
| Item | Amount |
|---|---|
| Drain rock (clean washed stone, 3/4 to 1½ in) | 4.32 cubic yards, 6.0 tons |
| Perforated pipe, 4 in | 75 ft (8 pieces of 10 ft) |
| Non-woven filter fabric | 375 sq ft |
| Soil to dig out | 4.2 cubic yards |
For a trench 12 in wide and 18 in deep, with 10% extra stone for uneven trench walls and settling. The stone is the trench volume less the space the pipe takes up, at 1.4 tons per cubic yard.
75 ft of drain, by trench size
Width × depth of the trench, with a 4 in pipe and 10% extra stone.
| Trench | Drain rock, cubic yards | Tons | Fabric, sq ft | Soil dug out, cubic yards |
|---|---|---|---|---|
| 8 × 12 in | 1.77 | 2.5 | 275 | 1.9 |
| 12 × 12 in | 2.79 | 3.9 | 300 | 2.8 |
| 12 × 18 in | 4.32 | 6.0 | 375 | 4.2 |
| 12 × 24 in | 5.84 | 8.2 | 450 | 5.6 |
| 18 × 24 in | 8.90 | 12.5 | 488 | 8.3 |
Where 75 feet of trench soil goes
Digging a 75 ft trench 12 in wide and 18 in deep brings out 4.2 cubic yards of soil, and loose soil takes up more room than it did in the ground, so allow extra for the pile.
Almost none of it goes back. The trench is filled with 4.3 cubic yards of stone, and only the top few inches are covered with soil or sod. Decide before you dig whether the spoil is being spread somewhere on the lot or hauled away.
Use clean, washed stone with no fines, wrap the stone (not the pipe) in the fabric, and make sure the drain has an outlet. The fittings, tools and steps are in the French drain materials list, and the method behind the stone figure is in how much gravel for a French drain.
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Tools & materials for this project
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Frequently asked questions
How much gravel do I need for a 75 foot French drain?
About 4.3 cubic yards, or 6.0 tons, of clean drain rock for a trench 12 in wide and 18 in deep with a 4 in pipe, including 10% extra. A 12 by 24 in trench takes 5.8 cubic yards.
How much dirt comes out of a 75 ft French drain?
About 4.2 cubic yards in the ground for a 12 by 18 in trench, and the pile is bigger once it is loose, so allow extra.
How much fabric for a 75 ft French drain?
About 375 sq ft of non-woven filter fabric, 60 inches wide, for a 12 by 18 in trench.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.