Bentonite for ponds

The most common mistake when using bentonite for ponds

Create an efficient bentonite seal for your pond or lake!

The most common mistake when using bentonite for ponds


Lonestar Minerals has been offering bulk bentonite for ponds and bentonite application services for over 20 years in Texas and the United States. Over this time, we have noticed a trend with inquiring customers for whom bentonite hasn’t worked in the past.


Bentonite is a natural clay that, due to its chemical composition, can absorb water up to 13 times its original size. When it absorbs water, it creates a sort of “mud” (that looks similar to pottery clay) that effectively seals the area under the pond, preventing underground filtrations and keeping the water inside the limits of the pond or lake.


In order to create a good bentonite seal, bentonite must be “trapped” inside the soil of the bottom of the pond; effectively expanding within the bottom of the pond and preventing the leakage of water to the underground or the sides of the pond. There are 3 different methods to apply the bentonite that have different effectiveness rates.

Method #1: Blanket Method(Pond Liner)
As its name states, the blanket method consists of removing 4-6 inches of soil from the bottom of the pond and depositing it at the edge of the pond. Then, spreading the bentonite throughout the surface of the bottom of the pond, creating a “blanket” of bentonite and finally covering the bentonite blanket with the removed soil. Compacting is the last step before filling the pond again.

Method #2: Mixed Blanket Method (Pond Liner – Soil with little clay)
Similar to the previous method, but instead of removing a layer of soil you rake or till within the top 4-6 inches of the soil at the bottom of the pond. The bentonite is applied to the surface and then it has to be tilled into the soil, aiming to create a homogeneus mix of soil and bentonite. Then we proceed to compacting and filling and it’s done.

Method #3: Sprinkle Method (Pond Sealer on Full pond)
This method should only be used in ponds or lakes that, for any reason, can’t be drained. Fish should be removed before applying granulated bentonite to the surface of the water. The bentonite granules sink and settle within the cracks, holes and crevices at the bottom of the pond, sealing of the leaks.


In order to create a tight seal, you need to apply the right amount of bentonite per square foot of area. A lot of people make the mistake of trying to economize by using less bentonite than recommended per unit of area. This only reduces the effectiveness of the seal and makes your investment worthless, as the pond or lake will continue to leak and lose water through the cracks into the underground.
In order to secure your investment, make sure you use the recommended amount per square foot. If you are hesitant and need to confirm the amount of bentonite required to seal your pond, use our Online Bentonite Calculator or click here to give our Technical Team a quick call. We are always able to help you figure out what’s the best solution for your leaking pond.

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Ponds with mistakes on bentonite application