Bentonite Pond Sealer is cost effective, non toxic and a long lasting solution for sealing ponds and lakes

Bentonite Pond Sealer is environmentally friedly and absolutely safe for stock, fish, wildlife and even for swimming.

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Pond Sealer Flow

How does bentonite pond sealer work?

Sand, rocky ground, rock formations and gravel leave small cracks and holes through which the water slowly seeps. Sodium Bentonite Pond Sealer is your best ally to solve the water loss problems. Bentonite will find its way inside those small holes and cracks of the soil, and then it will swell at the contact with water, thus creating a seal that will prevent water seepage, making it a great pond sealer and liner.


Bentonite is a mineral clay, milled to specific standards, that will blend seamlessly into the nature of your pond. It is free of chemical additions or hazardous materials and non toxic, therefore you can safely hold it in your hands with no harm. Use it for fish, duck, or wildlife ponds. It is especially ideal for stock and farm ponds because it won’t be damaged by the steps and weight of the stock or other animals.

Sodium Bentonite Lab Test Expanded Vs Normal - Lonestar GTC
Sodium Bentonite Lab Test Expanded Vs Normal
Installing Benonite pond liner on a new pond
Installing Bentonite pond sealer on a new pond

Bentonite Sealer is easy to apply in either dry or wet ponds (ponds that can’t be drained), is a 100% natural earth sealer, and is safe for fish, safe for plants, safe for stock, and safe for swimming. It is cost effective, as it is comparable in price to other similar sealing products and, when applied correctly, it will create a seal that will last for a long time.


You can use our Bentonite Calculator at the bottom of this page to obtain a better approximation of the amount of bentonite you require to seal your pond.

Bentonite Pond Sealer Application

Bentonite Clay Pond Sealer Application in a Retention Pond

Application is key for success. We can’t stress enough the importance of the correct product application. It is the difference between a full pond for years to come or headaches year after year.


It’s not uncommon for customers to call in because they have a leak in the dam area. In those cases, we use a method called the sprinkle method, where the bentonite pond sealer is applied over the water surface. We use this method for ponds that can’t be drained. The sealer will start to sink to the bottom, following the flow or current created by the leak through the water. It can be done for the whole pond, or only for a problematic area, in which case it is called spot treatment. Spot treatment is a variant of the sprinkle method, where the sealant is applied only to a particular area of the pond.

When there isn’t a single identified area for the pond leaks, we recommend drying the pond, when possible. For dry ponds, there are 2 methods. The first one is the blanket method, which requires removing debris to create a surface as smooth as possible, removing about 6 inches of soil, applying the amount of sealant required in an even layer and then covering the layer of sealant with the soil that was previously removed. Then it is ready to slowly add the water in.


The mixed blanket method requires to rake or till 6 inches of soil and then apply the sealant as if you were seeding or fertilizing. Rake again to mix the bentonite into the ground and compact the ground. Remember to add the water in a steady flow to prevent disturbing the layer of product you just created.


It is highly recommended to have a professional service for sealing a leaky pond or stop water seepage. If you require a turnkey service that can take care of diagnosing, sourcing and applying the materials to repair the pond, visit our Pond Repair Service page.

Benefits of using sodium bentonite clay as a pond sealer


Sealing leaks or full ponds with bentonite is cost effective, non toxic, environmentally friendly and long lasting. It is quite easy to apply, although it is important to get it right in order for the seal to be effective. Sodium bentonite keeps your pond as close as possible to a natural environment. Being a 100% natural clay, you add to the ground a component that will blend perfectly into the pond’s ecology and give you an excellent result for a very low cost and a very long time.


Sodium bentonite is a natural clay that swells up to 12 times its size. The bentonite is applied to the bottom of the pond and swells at contact with water, therefore creating a layer of compacted clay soil that will help hold water inside the pond. Unlike rubber or plastic liners, bentonite can fill any gap, slit or crevice, sometimes around a tree root or a rock. One of its biggest advantages? No puncture risk.


  1. Effective Seal – When correctly applied, the bentonite clay seal is very strong and long lasting.
  2. 100% Natural – You won’t be adding any artificially produced materials to the soil.
  3. Cost Effective – Comparable investment to other liners, lower long term maintenance costs.
  4. Absolutely Safe – Totally safe for stock, fish, ducks, wildlife, plants, swimming, etc.
  5. Puncture Free – Bentonite is an active liner that can repair small crevices or gaps by itself.

Bentonite vs Soilfloc


There are 2 categories of pond sealer products: active and passive. Bentonite is an active pond sealer, which means it interacts with the environment to create a watertight seal that prevents leakage. In the same category, we find polymeric pond sealants like Soilfloc, which makes them our best competition (yes, we respect them and we’re not afraid to talk about them).


Let’s start by explaining how polymeric sealant products work. The polymer molecule (which is called anionic polyacrylamide) is a man-made product that, as its name says, has negatively charged ions, giving the polymers ability to attract positively charged clay cations. So yes, they actually attract the existing clay in your pond for the sealing process! In combination with a man-made polymer. What do we think? Well, we think that if the clay alone can work for you, why use a man-made product? Of course, this depends on each particular case and while bentonite sealer might be best for some cases, soilfloc can beat us in other cases. It all depends on the customers project.


Polymer products usually come in parts, a format that requires you to apply part A and then, part B. With bentonite, you have a single application and that’s it. No parts, no complication.


Is there a better product choice between polymer sealants like soilfloc and bentonite pond sealer? We believe there is, but it will depend on your particular project needs and your personal interests. While polymer products may be required in some cases, if you are hesitant between these 2 types of pond sealer products give us a call. We will honestly tell you if bentonite is not the best choice for your project (yes, integrity is one of our core values).

Pond Sealer – The Lonestar Minerals Formula


Lonestar Minerals, using the expertise of more than 50 years in the field, has developed its own “formula” for pond sealers, using sodium bentonite as the only ingredient. We use a mix of different grain sizes, milled and packed at our ISO-9001 processing plant. We test each and every batch leaving our plant to guarantee its quality.


The mix of bentonite particles and granular bentonite allows us to take advantage of the properties of both grain sizes, helping reduce the amount of bentonite required per square foot* (*compared to other sources of bentonite clay for ponds).


We work with an extensive delivery network and can reach most states of the United States within 1-2 days. We have availability from a single 5-gallon bucket with 50 lbs of bentonite pond sealer up to full truckloads of bentonite for pond construction, delivered in paper bags or 3,000 pounds super sacks.


We pride ourselves in conducting our business with Integrity, providing truthful consultation services (yes, we will honestly tell you if bentonite is not the best solution for you) and operating under laws, legislation and policies. We value People, rather than things. Our main goal is to aid our customer’s success and to know our staff is proud to be working with us. Learn more about Lonestar Minerals in our About page.

What our customers are saying

“My business is simple. I design ponds. Lonestar has been my main supplier of bentonite for the past 7 years. They are honest, hard-working, and have never let me nor any of my clients down.


With pleasure, I sure do recommend them!”

Alex Hankins


“Lonestar Bentonite declares to have a high-performance product. The product seems to work as advertised. We’re very pleased with the results so far. Every day, it seems to be better. I highly recommend this product, as I tried other options on the market and didn’t work as well as this one.”

Pat Talamas


Need help with a leaking pond?

We provide full service to fix leaky ponds and lakes. We’ll supply the necessary equipment, operators, and mineral to seal your pond and offer you a turnkey job.








Lone Star GTC, LLC

Texas Wholesaler Supplier for Bentonite Mineral
17595 Blanco Rd. Suite 200, San Antonio, TX 78232



What are the benefits of using bentonite as a pond sealer?

Sealing leaks or full ponds with bentonite is cost effective, non toxic, environmentally friendly and long lasting. It is quite easy to apply, although it is important to get it right in order for the seal to be effective.

How much sealant is needed for a 1 acre pond?

The short answer is between 30 and 80 tons of bentonite, to line the whole pond.
The most important factor to determine the amount of bentonite pond sealer required is the type of soil of your pond. Depending on it is how much bentonite pond sealant we recommend applying per square foot.

How much bentonite is needed to seal a pond?

The short answer is between 30 and 80 tons of bentonite, to line the whole pond. That said, this is based on a pond that has measurements of 208 feet x 208 feet and 8 feet depth. It is quite a large pond, and the exact amount of sealant will depend on the type of soil of the pond bottom the more porous it is, the more product will be required to create and effective and long lasting seal. The pond sealer itself it’s an inexpensive material, so don’t be afraid to Request a Quote.

Here are some reference values that can help you estimate the required amount of bentonite to seal any area (based on the Lonestar Minerals quality bentonite mix-mesh for ponds). Or, if you prefer, we have available a Bentonite calculator to easily approximate the amount of bentonite required for your pond.

Soil condition → Pond sealant per sqft
Rock or gravel → 3.0 to 3.5 lbs/sqft
Clean Sand → 2.5 to 3.5 lbs/sqft
Silty Sand → 2.0 to 2.5 lbs/sqft
Sandy Silt 20% Clay Min → 1.5 to 2.0 lbs/sqft
Clay Soil → 1.0 to 1.5 lbs/sqft

How much bentonite do you need?

Pond Sealer Page - Calculator

Bentonite Calculator

Please, enter your pond measurements, deepest point, and soil condition to find out [approximately] how much bentonite you would need to fix your leaking pond.

Type of Soil of your Pond *
Pond Shape *
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