Bentonite Guides
Why Sodium Bentonite Is the Right Choice for Dam Sealing
Sep
Quick answer: Sodium bentonite swells to several times its original volume when wet and can reduce seepage in suitable, properly installed soil treatments. Bentonite Pro supplies fines in 1.2 tonne bulk bags and uses a 30 kg/m² company standard, subject to site assessment.
Why sodium bentonite for dam sealing?
Sodium bentonite is a swelling clay. When hydrated, it expands to several times its original volume and can reduce the permeability of suitable treated soils.
Bentonite can be used in suitable dam and pond treatments. It is not a universal substitute for repairing structural faults or for other lining systems; diagnose the cause of water loss first.
How does sodium bentonite actually seal a dam?
Hydrated bentonite occupies pore spaces within a properly prepared treatment, helping reduce seepage. Performance depends on soil and water conditions, installation and protection of the treated layer.
What application rate should I use?
Bentonite Pro’s standard application rate is 30 kg/m². Confirm soil suitability, the cause of leakage and the installation method before ordering or starting work. This company standard is not a rate specified in the product sheet or a universal guarantee of sealing. Our product is fines, not the separate granular grade. See How It Works for mixed and pure blanket methods and their different compaction sequences.
What makes a high-grade sodium bentonite?
The product specification sheet gives typical montmorillonite content above 90%, cation exchange capacity above 90 meq/100 g and a swell index of 7 to 16 mL/2 g on an as-is basis. Our fines are nominally below 1.25 mm. The swell index is not a dry-volume expansion ratio, and purity alone does not establish whether a treatment suits a particular dam.
How much bentonite will I need?
| Surface area | Bentonite needed (at 30 kg/m²) |
|---|---|
| 200 m² | 6,000 kg (6 tonnes) |
| 500 m² | 15,000 kg (15 tonnes) |
| 1,000 m² | 30,000 kg (30 tonnes) |
Measure the total surface area you’re sealing (floor plus walls), multiply by 30 kg/m², and add a 5 to 10% preliminary allowance, subject to confirming site conditions and the treated area.
Choosing the right amount for your job
Bentonite Pro supplies sodium bentonite fines in 1.2 tonne bulk bags, delivered across NSW, VIC and QLD. See How It Works for installation guidance and limitations.
Can bentonite be applied in stages?
Stage the work only under a site-specific plan that maintains a continuous treated layer and protects completed areas from erosion and disturbance. Compact each section as required by the chosen method; do not assume that separate, unconnected patches will seal the whole dam.
Does the application rate change for ornamental or garden ponds?
Bentonite Pro uses the same 30 kg/m² company standard for preliminary pond quantities, subject to checking site suitability and the treatment method. The current product is supplied in 1.2 tonne bulk bags; contact us to discuss whether that pack size suits your job.
How long does a correctly applied bentonite seal last?
Service life depends on soil and water conditions, installation quality and protection from erosion, roots, burrowing animals, stock traffic and drying. A correctly selected and installed treatment can provide ongoing seepage control, but the product specification does not establish a guaranteed service life.
Not sure which quantity suits your dam or pond? Get in touch with Bentonite Pro.
For bulk bag prices, coverage per bag and indicative delivered costs to regional towns, see the sodium bentonite delivered price guide.
