Drainage Aggregates, Filter Rock & Gabion Rock - East Coast Tasmania
Drainage that performs properly is one of the most important and least visible parts of any construction or landscaping project. The right aggregate around a pipe, behind a retaining wall, or in a drainage system is what determines whether water moves the way it should - and whether the structures around it remain stable over time.
St Helens Quarries supplies drainage aggregates, filter rock, and gabion rock produced from our own quarries and delivered across St Helens, Scamander, St Marys, Fingal, Scottsdale, Derby, Bicheno, and the broader East Coast and North East Tasmania. All drainage aggregates are sourced from a high-quality quarry with a Polished Stone Value (PSV) of 57 - confirming durability and skid resistance in demanding applications.
We supply plumbers, builders, civil contractors, landscapers, and rural landholders across the East Coast regularly. If you're not sure which product suits your drainage application, call us - the right aggregate size makes a real difference to how a drainage system performs.
DRAINAGE AGGREGATES
40mm Drainage Aggregate
Our largest drainage aggregate - robust, free-draining, and suited to applications where high water flow capacity is needed alongside structural strength.
Drainage: Ideal for trench backfilling, septic system surrounds, and stormwater management systems where fast, reliable water movement is required. The size allows excellent flow-through while maintaining stable support around pipes.
Construction: Used as ballast and in heavy-duty concrete mixes where strength and stability are the priority.
Good for: septic systems, deep drainage trenches, construction ballast, heavy drainage applications.
20mm Drainage Aggregate
A versatile, commonly specified drainage aggregate that balances drainage performance with good compaction characteristics.
Drainage: Ideal for backfilling trenches around PVC and agricultural pipes, surrounding stormwater drains, and drainage installation behind retaining walls. Reliable water flow with structural support.
Construction: Widely used as a concrete base layer, in concrete mixes, and as a stable base for driveways and pathways. Strong compaction and load-bearing capacity.
Good for: pipe surrounds, retaining wall drainage, driveway bases, concrete mixes, pathway bases.
14mm Drainage Aggregate - PSV 57
A high-specification drainage aggregate sourced from a quality quarry with a Polished Stone Value rating of 57 - confirming excellent durability and skid resistance in applications where surface performance matters.
Construction & Infrastructure: Suitable for pipe backfilling and bedding, providing stable support while maintaining drainage around services.
Specialised Applications: Ideal for sub-surface drainage systems, tank installations, and as infill for synthetic turf installations. Also used in polished concrete finishes for both indoor and outdoor spaces.
Surface Sealing: Commonly specified in spray seal (bitumen) applications for low-traffic roads, delivering a fine, durable surface texture.
Good for: pipe bedding, synthetic turf infill, spray sealing, polished concrete, sub-surface drainage.
10mm Drainage Aggregate - PSV 57
A finer drainage aggregate well-suited to plumbing applications, spray sealing, and polished concrete. PSV 57 rated for durability and skid resistance.
Drainage: Used by plumbers for drainage trenches, surrounding PVC and agricultural pipes, and behind retaining walls. Effective water flow with structural integrity maintained.
Surface Sealing: Suitable for spray seal applications on low-traffic roads, producing a fine, consistent surface.
Specialised Applications: Works well in polished concrete finishes where a finer, smoother aggregate is required.
Good for: plumbing drainage, retaining wall drainage, spray sealing, polished concrete.
7mm Drainage Aggregate - PSV 57
The finest in our drainage aggregate range - highly versatile and used across a wider range of applications than its size suggests.
Drainage & Plumbing: Backfill for drainage trenches, around agricultural pipes (Agline), and behind retaining walls. Consistent, effective water management.
Concrete Production: Suitable for concrete mixes where a finer finish or greater detail is required.
Construction Bases: A compactable, stable sub-base for artificial turf, paving, and light-traffic driveways.
Surface Sealing: Used in spray seal applications for low-traffic roads.
Good for: Agline surrounds, paving sub-base, artificial turf, concrete mixes, spray sealing.
FILTER ROCK
Filter Rock - 40mm to 150mm Rock Spalls
A premium crushed stone aggregate with open grading that allows high water flow while acting as a heavy-duty barrier for drainage and erosion management. Larger than drainage aggregate, filter rock is suited to civil and structural applications where both drainage capacity and physical strength are required.
Good for: large-scale drainage systems, erosion control, civil construction drainage, structural landscaping.
GABION ROCK
Gabion Rock - 100mm to 250mm
Hard-wearing, angular rock sized for gabion cage and basket construction, retaining walls, creek line reinforcement, and architectural landscaping features. The angular form of the stone means it locks together inside the cage structure, resisting movement under pressure while maintaining the permeability that makes gabion structures effective at managing water.
Good for: gabion baskets, retaining walls, creek bank stabilisation, architectural landscaping.
CHOOSING THE RIGHT DRAINAGE PRODUCT
Drainage aggregate selection comes down to the flow rate required, the structural demands of the application, and the size of material needed to support adjacent pipes or structures.
For plumbing and pipe surrounds, 7mm, 10mm, and 14mm aggregates are the standard range -finer material provides stable, close support around pipes while still allowing water to move freely. For retaining wall drainage and larger civil drainage systems where higher flow capacity is needed, 20mm and 40mm aggregates provide the open grading that moves water quickly. For larger structural drainage and erosion management, filter rock handles the volume. For gabion construction and creek line reinforcement, gabion rock provides the weight, angularity, and durability the structure needs.
If you're specifying drainage for a project and want confirmation on the right product and quantity, call us. We supply to specification and can advise on what the application requires.
All materials weighed with trade-approved accuracy. Delivery across the East Coast and North East Tasmania.
Frequently Asked Questions
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For standard residential plumbing drainage around PVC and ag-pipes, 7mm or 10mm aggregate is the most commonly specified product. It provides close support around the pipe while allowing reliable water movement. For larger stormwater pipes, 14mm or 20mm is more appropriate. If you're unsure, describe your application and pipe diameter and we'll confirm the right size.
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Drainage aggregate (7mm–40mm) is used in plumbing, pipe surrounds, retaining wall drainage, and general construction drainage where a graded, close-contact aggregate is needed. Filter rock (40mm–150mm) is a larger, open-graded product designed for high-volume water flow and structural drainage applications — erosion control, large drainage systems, and civil projects where the drainage load is significantly higher. They serve different scales of drainage requirement.
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A standard residential retaining wall drainage layer is typically 300mm wide behind the wall for its full height. For a 10-metre wall at 1 metre height with a 300mm drainage zone, you'd need approximately 3 cubic metres of drainage aggregate. Call us with your wall dimensions and we'll calculate it accurately.
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Yes. Our 7mm, 10mm, and 14mm drainage aggregates are all used in spray seal (bitumen) applications for low-traffic roads. All are sourced from a quarry with a PSV rating of 57, confirming the skid resistance required for sealed road surfaces.
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Yes - we supply plumbers, builders, electricians, landscapers, and concreters across the East Coast and North East regularly. Trade accounts available. Call to discuss.