Quick answer: Use Bentonite Pro’s recommended 30 kg/m² rate to calculate your order, then round up to whole 1.2 tonne bags. Confirm soil suitability, the cause of leakage and the treatment method before proceeding.
How much bentonite do you actually need?
For preliminary ordering, multiply the total area to be treated by Bentonite Pro’s recommended application rate of 30 kg/m². Include the dam floor and any walls to be treated; quantity alone does not establish whether bentonite is suitable for the leak.
Does soil type change the application rate?
Bentonite Pro’s recommended application rate is 30 kg/m². Confirm soil suitability, the cause of leakage and the installation method before ordering or starting work. This recommended rate is not a rate specified in the product sheet or a universal guarantee of sealing.
How do you calculate the total bentonite needed for a project?
- Measure the surface area to be sealed: length × width for the base, plus batter (sloped wall) area if you’re sealing the sides too.
- Multiply the total square metres by Bentonite Pro’s recommended application rate of 30 kg/m².
- Add a 5 to 10% preliminary allowance, subject to confirming site conditions and the treated area.
Sodium bentonite is a swelling clay that expands to several times its original volume when wet. The product sheet records a typical swell index of 7 to 16 mL/2 g, which is not a dry-volume expansion ratio.
How much bentonite for common dam and pond sizes
| 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) |
Allow for measured site conditions and round the calculated requirement up to whole 1.2 tonne bags. Confirm the quantity before dispatch rather than relying on a universal buffer.
Buying the right amount for your project
Bentonite Pro supplies sodium bentonite fines in 1.2 tonne bulk bags, delivered across NSW, VIC and QLD.
For 500 m² at 30 kg/m², you need 15,000 kg. This is 12.5 bags of 1,200 kg, so order at least 13 whole bags before an allowance. Including a 5 to 10% allowance requires 14 whole bags. Confirm the treated area and allowance before ordering.
What happens if you under-apply bentonite?
An uneven or insufficient treatment may leave seepage paths. Using enough material is only one requirement: soil suitability, continuity of the treated layer, cover and compaction also need to be checked.
Can you apply bentonite 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 bentonite application rate change for ornamental or garden ponds?
Bentonite Pro uses the same recommended 30 kg/m² rate 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.
Need help sizing your bentonite order? Get in touch with Bentonite Pro.
For the price per tonne, coverage per bag and how freight to your address is worked out, see the sodium bentonite delivered price guide.