Gravel for Drainage

Gravel for Drainage

5 min read · Updated June 2026

💧 Quick Answer: Use #57 Washed Stone

Clean 3/4" crushed stone (#57) is the best all-purpose drainage gravel. It has angular edges that resist shifting, large voids for water flow, and no fine particles to clog over time.

Best Gravel by Drainage Application

Drainage Use	Best Gravel	Depth	Notes
French drain	#57 washed crushed stone	6–12" around pipe	Wrap pipe in drainage sock first
Surface drainage bed	#57 or #5 (1") stone	4–6 inches	Use fabric underneath to separate from soil
Drywell / soakaway	#57 or larger river rock	12–24" around barrel	Larger stones = better flow capacity
Raised bed drainage layer	#57 or pea gravel	2–4 inches	Goes under growing medium in raised beds
Rain garden border	Pea gravel or #57	3–4 inches	Decorative + functional at pond edge
Under concrete slab	#57 compacted base	4–6 inches	Compacted #411 preferred for structural slabs
Around foundation / basement	#57 washed stone	6–12" against wall	Critical: use drainage fabric to prevent soil migration

French Drain Installation Guide

What is a French drain? A perforated pipe buried in a gravel-filled trench that redirects water away from problem areas. Solved millions of waterlogged yard and basement problems.

1
Excavate the trench: Dig 12 inches wide × 18–24 inches deep along the planned drain path. Slope the trench at least 1% (1 inch drop per 8 feet) toward the outlet.
2
Line with drainage fabric: Line the trench sides and bottom with drainage fabric. This prevents soil migration into the gravel — the biggest cause of French drain failure.
3
Add 3 inches of #57 gravel base: Place clean #57 crushed stone (no fines) in the trench bottom, 3 inches deep.
4
Lay perforated pipe: Place 4-inch perforated pipe on the gravel bed, holes facing down. Connect sections and direct outlet to daylight, dry well, or storm drain.
5
Fill with #57 gravel to 3" below surface: Cover the pipe completely with clean #57 gravel. No fine material — fines clog the pipe over time.
6
Wrap fabric and backfill: Fold drainage fabric over the top of the gravel. Backfill with soil and restore surface (lawn, mulch, or gravel).

Why "Clean" Gravel Matters for Drainage

✓ Clean (Washed) Gravel

✓ Large void spaces between stones
✓ Water drains freely
✓ Won't clog over time
✓ Best for French drains and drainage systems

✗ Dirty Gravel (with fines)

✗ Fine particles fill the voids
✗ Restricts water flow
✗ Can compact and become impermeable
✗ #411 crusher run — great for driveways, bad for drainage

Calculate your drainage gravel

Enter trench or bed dimensions for instant cubic yards and tons.

Open Gravel Calculator →

Frequently Asked Questions

What is the best gravel for drainage?

#57 washed crushed stone (3/4 inch) is the best general-purpose drainage gravel. It's angular enough to resist shifting, large enough to allow good water flow between stones, and clean (no fine particles that would clog the void spaces). For French drains specifically, use clean #57 around the perforated pipe.

How deep should drainage gravel be?

For a French drain, fill the trench with 6–12 inches of gravel around and over the perforated pipe. For general surface drainage beds, 4–6 inches of gravel is sufficient. For rain garden borders and swales, 3–4 inches works well.

Does gravel help with drainage?

Yes — gravel creates void spaces between stones that allow water to move through much faster than soil. A 6-inch gravel layer can drain water 10–100× faster than compacted soil. This is why gravel is essential for French drains, drywell systems, and raised bed drainage.

Can you use pea gravel for a French drain?

Pea gravel works but isn't ideal for French drains. Its smooth, round shape provides less resistance than angular stone, meaning it can shift and rearrange over time. Angular #57 crushed stone is the preferred material because it stays in place and has better long-term drainage performance.

How much gravel do I need for a French drain?

A typical French drain trench is 12 inches wide and 18–24 inches deep. Per 10 feet of length, you need approximately 0.5–0.7 cubic yards of gravel. Use our gravel calculator with your exact trench dimensions for precise quantities.