LINE YOUR POND OR REPAIR LEAKS WITH BENTONITE CLAY POND LINER
The most effective, natural sealer for ponds and reservoirs.
Sodium bentonite is a versatile, natural montmorillonite clay with exceptional swelling and sealing capabilities. Its notable feature is its ability to absorb many times its weight in water, causing it to swell and create a densely bonded, impermeable barrier in the soil. This barrier prevents water from seeping through, creating an effective sealant for ponds and reservoirs.
Being a natural clay, sodium bentonite is environmentally friendly and non-toxic. It does not introduce harmful substances into the water or adversely affect aquatic life or wildlife. It is perfectly safe for swimming, plants, fishes, livestock and pond life, and provides an environmentally-friendly alternative to plastic liners.
Uses:
- Lining small and large bodies of water such as ponds, lakes, canals and reservoirs
- Repairing leaks in ponds, lakes and reservoirs
- Dam sealing
- An ideal solution for civil engineers, contractors, developers, homeowners, golf courses, farm owners and event venues
POND LINER:
Sodium bentonite swells to several times its size when wet, which creates an effective impermeable seal at the bottom of the pond. By lining the bottom of the pond and banks with bentonite clay, leaks or seepage in the pond or lake area are prevented.
Browse our BENTONITESEAL pond liner product range here.
How much do I need?
The amount of bentonite required to create an effective seal varies according to the soil type and whether you're able to fully drain the pond to line it. Soil types with a naturally high clay content will require less bentonite granules than sandy soil or gravel. Additionally, if you're unable to extract all of the water from the pond or lake prior to adding the bentonite (for example, due to a natural spring or groundwater), a higher volume of bentonite will be required.
Approximate amount of sodium bentonite granules required:
| SOIL TYPE | APPROXIMATE AMOUNT REQUIRED* |
| Fair clay | 10kg per square metre |
| Poor clay | 15kg per square metre |
| Silty loam | 15 - 19kg per square metre |
| Sand | 19 - 25kg per square metre |
| Sand & gravel | 29kg per square metre |
| Gravel & rock | 29 - 40kg per square metre |
*increase these amounts if you are unable to fully drain the pond/lake prior to application
Key benefits over polymer pond liners:
- Highly effective alternative to traditional pond liners that does not damage the natural ecosystem
- High resistance to water pressure
- Maintains plasticity; does not become brittle over time
- Easily applied by hand/farm machinery
- A plastic-free product supplied in plastic-free packaging
- No risk of punctures or tears in the lining by livestock or wildlife
- Cost-effective alternative
- Can last for decades with minimal maintenance
How to apply sodium bentonite granules:
First the area needs to be cleaned. The bentonite will need to be compacted, so any debris that is likely to affect this process needs to be removed.
There are two options for applying the bentonite:
1. The Blanket Method
This involves removing the top layer (15-20cm) of soil and depositing it on the banks of the pond/lake, then spreading a layer of bentonite as evenly as possible over the pond including the banks (see the table above for guidance on the quantity to use). Then spread the soil that was deposited on the banks over the bentonite clay and use machinery to compact the soil and sandwich the bentonite layer. You can then fill the pond/lake slowly, taking care not to disturb the bentonite layer.
The bentonite will absorb water initially before swelling and creating an impermeable barrier - this can take up to five days so expect the water level to drop initially and top up accordingly.
2. The Mixed Blanket Method
Instead of removing the top layer of soil, till the soil to about 20-30cm depth. Then apply the bentonite and mix into the soil (using the same method as tilling the soil) until it is evenly mixed. Use machinery to compact the soil/bentonite layer. Slowly fill the pond or lake, taking care not to disturb the new layer.
The bentonite will absorb water initially before swelling and creating an impermeable barrier - this can take up to five days so expect the water level to drop initially and top up accordingly.
Handy resources:
POND SEALANT:
Due to its swelling capability and ability to create a densely bonded, impermeable gel barrier in the soil, sodium bentonite is the most effective sealer for fixing leaks in ponds, lakes and dams.
The bentonite clay can be sprinkled over the pond either by hand in a boat over the leaking region, or by farm machinery/pneumatic trailer for a wider coverage.
The clay granules will sink after some time and create a gel-like seal over the bottom of the pond.
Browse our BENTONITESEAL pond/lake sealant product range here.
FAQ's:
I have a pond that was holding water well but the water level has dropped a couple of feet more recently, suggesting a leak. Do you recommend bentonite clay granules to plug the leak?
Due to its swelling capability and ability to create a densely bonded, impermeable gel barrier in the soil, sodium bentonite is the most effective sealer for fixing leaks in ponds, lakes and dams.
For a pond filled with water: the bentonite clay granules can either be sprinkled over a pond with water and the flow of water will naturally pull the swelling granules to the leaking point, where the swollen clay will plug the leak.
If you are able to drain the pond: the bentonite granules can be mixed with water to form an impermeable gel and applied to the leaking region as a filler.
When filling a hole in a pond, should I apply the bentonite granules in their dry form, or should I mix the granules with water first?
If the pond is able to be drained to expose the leaking region, we recommend mixing the bentonite clay granules with water first and then spreading the mixture over the affected area.
If the pond is full with water, the dry granules can be spread over the pond. The granules will be pulled towards the leak by the flow of water, settle and form an impermeable muddy gel-like layer to plug the leak.
Should I apply more bentonite clay granules to steep banks and less to flatter regions?
Yes. Due to gravity, some granules applied to steeper banks may migrate downslope.
If the pond is empty, best practice is to lightly till or cultivate the upper soil layer on the banks after applying the bentonite, then compact the soil. This helps incorporate the granules and keeps them in place. We also recommend applying a slightly higher dosage on the banks.
If the pond is already full, apply a greater proportion of the granules over the bank areas, as these locations are typically more prone to leakage.
Could plant roots cause the seal to fail and lead to the pond leaking over time?
Plant roots can, over time, create pathways through the clay that may result in minor seepage. As a precaution, it can be beneficial to keep a few additional bags of bentonite granules on hand. If any seepage occurs, the granules can be lightly sprinkled over the pond surface; the escaping water will naturally draw the bentonite into the affected area, where it will swell and help seal the leak.
It is worth noting that the ability for vegetation to establish through the clay is often considered a key advantage of sodium bentonite compared with traditional synthetic liners. Because sodium bentonite is a natural clay, it supports the development of a more natural pond environment. Tree and plant roots can grow within it, and the material’s excellent moisture retention and nutrient-holding properties can actually benefit surrounding vegetation. For this reason, bentonite is also commonly used in agriculture to improve the condition of sandy and peaty soils.
What type of compactor do you recommend for compacting the soil and bentonite clay?
For smaller projects, a vibratory jumping jack rammer is recommended, as it provides deeper and more effective compaction. A vibratory plate compactor may also be used, although it does not achieve the same compaction depth as a jumping jack. For larger ponds, lakes, and reservoirs, the use of a sheepsfoot roller compactor is advised.