Description

Drainage Gravel 20mm

Handle demanding drainage conditions with Drainage Gravel 20mm, a coarse aggregate designed for high-flow drainage, retaining walls and large-scale water management applications.

Made from crushed blue metal, this gravel features larger 20mm stones that create maximum void space, allowing water to flow freely and efficiently, making it the most commonly used drainage gravel for bulk applications.

Its size and strength make it ideal for both residential and commercial projects, particularly where heavy water flow or structural drainage is required.

Available Sizes

This product is available in multiple sizes to suit different drainage applications:

• 5mm Drainage Gravel — Ideal for behind pipes, ag lines and tight access areas
• 10mm Drainage Gravel — Most popular for general drainage and all-round use
• 20mm Drainage Gravel — Best for high-flow drainage and retaining wall backfill

Key Features & Benefits

Maximum drainage performance — Larger stones create greater voids for fast water flow and reduced blockage.

Ideal for high-flow areas — Perfect for retaining walls, soak wells and bulk drainage systems.

Strong and durable material — Crushed blue metal provides long-term structural stability.

Prevents water build-up — Helps reduce hydrostatic pressure behind walls and structures.

Versatile application — Suitable for drainage, landscaping and construction projects.

What It’s Used For

Behind Retaining Walls — The preferred choice for draining large volumes of water and reducing pressure build-up.

Stormwater & Drainage Systems — Ideal for high-capacity drainage zones and water diversion areas.

Soak Wells & Trenches — Suitable for bulk water movement and dispersion.

Driveways & Heavy Areas — Can be used in applications requiring both drainage and strength.

Landscaping & Feature Areas — Also suitable for decorative or functional gravel use.

Why It Performs Better

Drainage Gravel 20mm performs exceptionally well due to its larger particle size, allowing it to:

• Create large voids for rapid water movement
• Prevent clogging in high-flow conditions
• Reduce water pressure behind retaining structures
• Maintain stability under load

This makes it the best choice for demanding drainage applications, especially where smaller aggregates may restrict flow.

Important Product Characteristics

Coarse 20mm aggregate — Designed for bulk drainage, not fine or precision work.

High void ratio — Provides superior water flow but less compaction than smaller sizes.

Not ideal for tight spaces — Smaller gravel (5–10mm) is better for pipe backfill and confined areas.

Natural variation — Colour and particle size may vary between batches.

Installation Tips

• Use behind retaining walls to relieve water pressure
• Combine with ag pipe and geofabric for optimal drainage systems
• Install at appropriate depth depending on application
• Do not over-compact — maintain void space for drainage performance

Practical Information

This product is supplied as a bulk material, with delivery options including Bulka Bags (1m³) for sites with restricted access.

Due to the natural materials used, colour and size may vary between batches, which is normal.

Also available in Bulkabags – Click Here

Bulka Bags