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Natural Waterscapes

Granular Bentonite Clay for Pond Sealing - 45 pounds

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  • Sodium Bentonite clay pond sealer
  • Granular bentonite for ponds
  • Sodium bentonite clay
  • Pond Sealer Bentonite
  • Application rate for sodium bentonite clay to fix pond leak
  • minus 8 mesh sodium bentonite pond clay


Sodium Bentonite Clay for sealing ponds - 45 lb bag

One 45 pound bag = 0.63 cubic feet  Covers 9 square feet at 6 pounds per square foot.

Bentonite clay is a natural expanding clay sealant that when exposed to moisture can expand 15X or more creating a very effective pond sealant when applied correctly. 

Bentonite for Pond Sealing FAQ

Sodium Bentonite Source

Our bentonite clay is provided in granular form directly from the processing facility in Northeastern Wyoming. 

Bentonite Clay Application Rates for pond/lake bottoms

To properly apply bentonite to seal a pond, the pond must be drained and the bentonite clay then incorporated into the soil of the pond bottom and sides. The application rate for bentonite ranges from 2 pounds to more than 5 pounds per square foot depending on the soil characteristics. For clayey and silty soils, 2 pounds per square foot MAY be sufficient. For sandy soils 4 pounds MAY be sufficient and for soil containing gravel and rock, in excess of 5 pounds will be required to obtain a seal. Once the bentonite is applied, the soil should be disk harrowed to mix the soil and bentonite and then compacted.

Alternatively, a continuous blanket of bentonite can be applied to the soil and then carefully covered with clean soil or sand to prevent the clay from mobilizing into the water column. Placing the bentonite in a confined layer is far more effective as it forces the clay into adjacent soil pores creating a more effective seal.

Pond or Lake Dam Repair

For a leaking pond embankment, if the location of the leak has been identified, it may be possible to construct a core trench in the embankment to slow the leak. To install a core trench, excavate a minimum 12 inch wide trench to at least 3 feet below the pond bottom elevation. The trench should be located as far back from the pond edge as possible while still remaining on the flat top of the embankment.

The goal is to create an impervious core in the embankment which will not allow water to pass through. This impervious core can be created in a number of ways. Bentonite can be mixed with the excavated soil at a rate of 30% bentonite and 70% native soil. The material should be placed back in the trench and compacted with a trench roller, plate tamper, or excavator bucket in 6 inch lifts. 

Sealing around Leaking Outlet pipes

 Excavate at least 24" around the leaking outlet pipe.  Replace the excavated soil with 100% Wyoming Sodium Bentonite Clay.  Replace the native soil around the bentonite clay seal and compact in place with a trench roller or jumping jack compactor.

Ships via standard ground parcel service.   


Bentonite Clay Reviews - What our Customers Say

Awesome Dam hole plugging

Your sodium bentonite clay worked awesome! I had a specific area, perhaps started by a muskrat years ago, sucking water and soil right through the dam lowering the pond about a foot so it wouldn't go over our outlet. We dug a trench with an excavator about 10 feet long x 1 foot wide x 4 feet deep. I only used 2/ 45 lbs. bags by mixing it with clay dirt 1/8 parts approximately. Now, just a few days later the overflow is overflowing again without any significant rainfall. I've tried other ways half a dozen times but never did it fill back in so well nor did it last. - Daniel G.

Works as Promised 

hope this works as good as the first one did. will use again if needed. stoped leak for over 2 years. - Don W.

It stopped our pond leak!

We had been losing water out of our 1/3 acre pond but we couldn’t drain it to mix bentonite in with the soil because it’s stocked. We bought five 45-lb bags and spread it generously along 3/4 of the banks and throughout the water. It immediately made a difference. It’s been sunny and hot since we applied it and our pond has maintained its level.  It was worth every penny! - Keena W.

Pond water leak was stopped 

Product worked great, Water leak was stopped in a few hours. Worth the price. - Glen P.

Very Easy

Ordered 5 bags of bentonite and they arrived on time as promised - Kathleen R.

Worked like a Charm

So, the Natural Waterscapes Granular Sodium Bentonite Clay for Pond Sealing has fixed my leaking pond! The leak was around the concrete drain. The leak was so bad there was a large cavity about four feet deep and 30 feet long running along the outside of the drainpipe. I dug out the area around the drain about a two foot cube, that was the beginning of the big cavity. I mixed the bentonite clay in with the dirt I had dug up and tamped in around the concrete drain. I then filled in the rest of the cavity with dirt from the farm. The pond filled up after several rains and has been at its normal level for two weeks. There is no discernible drop in the water level. For reference my pond is roughly 150 feet in diameter and 10 feet deep at the deepest point. I would recommend making sure you order enough as the one bucket barely did my project. I would say I removed 5-6 large wheelbarrows full of dirt from the leaking area and then mixed the clay in. If I had to remove anymore dirt I don't think one bucket of bentonite clay would have been enough. - les M. 

This stuff works!

I used this bentonite last fall to seal a leak in a pond dam. There was a CMP overflow for the pond, and a leak had developed under the pipe. I removed the pipe, backfilled with dirt mixed with this bentonite, and the pond level rose a foot overnight. No leaks. We had developed an alternate overflow to protect the dam. I'm going to order more for another dam project. - Kansas B.

It works on Duck Ponds

My duck pond is holding water after using your product and the ducklings are having fun and are very thankful - Dena H.

Been using Bentonite for years

I have been using bentonite for years to seal leaks. The material is easy to use and very effective. The wetter it gets, the more it seals. - John B.

Works well with concrete-clay mixture

Pond sealed up nicely. I didn't mix with the soil though. I actually made a slurry with the clay and mixed in with my concrete. It's a small existing pond my father built almost 30 years ago,, that I've battled to seal back up for any extended period of time. This clay is apparently a great additive for strengthening concrete mixtures as long as a proper slurry of the granules is made and proper ratio is used in the mixture. Have had zero leakage issues since incorporating this product. Was about ready to turn the thing into a flower bed lol. - Chris D.

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