Bentonite clay granules expand to several times their size and bond together when wet, forming an impermeable barrier against water. This makes sodium bentonite a highly effective pond liner and sealant.

We at Bentonite International Ltd. provide BentoniteSeal, a natural and eco-friendly alternative to plastic pond liners. Our sodium bentonite clay granules expand when wet, forming a strong, impermeable barrier that prevents water leakage. This makes it ideal for lining ponds, lakes, and reservoirs, as well as repairing leaks and sealing dams. BentoniteSeal is safe for aquatic life and offers a cost-effective, durable, and environmentally friendly solution for your pond projects.  Sodium Bentonite (BentoniteSeal) is supplied as granules, when wetted these granules expand to form an impermeable layer, it is easy and quick to create a watertight pond or reservoir or even to repair an existing pond or dam.  This is a robust material, there are no risks of tears and UV sunlight damage, you can plant into it and allow livestock to walk in it.  It will never wear out.  It is the perfect natural solution and will make a superb natural swimming lake or pond.

Bentonite is perfectly safe for swimming, plants, fishes and pond life, and provides an environmentally-friendly alternative to plastic liners.

Quality products backed by scientific testing

Our sodium bentonite granules are put through rigorous quality checks, including observation under the microscope to ensure consistency between batches and superior performance.

SPECIFICATIONS:

• Sodium bentonite
• Colour: grey
• Size: 0.5 - 4mm granules
• Moisture ≤ 3%
• Absorbency ≥ 450%
• pH 9.5
• Supplied in 1 tonne bulk bags with handles and inner PE sealed lining. The bag also features a bottom opening for easy pouring. Each 1 tonne bag is delivered on a pallet.
• ISO9001, ISO14001 and ISO18001 certified processing plant
• For guidance on the volume required and application methods click here

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 and homeowners

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
• No risk of punctures in the lining by farm animals or wildlife
• Cost-effective alternative

>> Learn more about using sodium bentonite as a pond liner/sealant here (including guidance on the volume required, application methods, etc).

>> See our delivery policy here for further details on how this product is delivered

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.