Pondlock™ Granular Bentonite Clay – High Expansion Pond Sealant

Pondlock™ is a premium-grade, natural granular bentonite clay engineered specifically for pond sealing applications. Packaged in durable 3,000 lb bulk sacks, each unit delivers approximately 42 cubic feet (1.56 cubic yards) of material. This high-performance clay expands up to 15 times its dry volume when hydrated, forming a dense, self-sealing barrier that effectively reduces water loss in ponds, lakes, and other water features.  The Free Swell Index (ASTM D5890)of 30 ml exceeds the Natural Resource Conservation Service (NRCS) standard of 22 ml or greater specified in Conservation Practice Standard 520.

Packaging & Shipping:

• Each 3,000 lb sack is equipped with a bottom drawstring discharge port and four top lifting loops for secure, stable handling.
• Less-than-truckload (LTL) orders are palletized and shipped in enclosed vans.
• Full truckload (FTL) orders ship via flatbed freight and may be delivered without pallets.
• A full truckload contains 15 sacks (45,000 lbs total).

Pondlock™ offers a reliable and eco-friendly solution for sealing ponds naturally. Its superior 15X expansion capacity ensures effective coverage and long-lasting performance when applied correctly.

Bentonite for Pond Sealing FAQ

Sodium Bentonite Source

Our bentonite clay is shipped directly from the mine 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.

Detailed Sodium Bentonite Application Instructions

For best results test application rates with your soils by treating a small area at the anticipated application rate.  Drive a 12" or larger diameter smooth wall pipe at least 8" into the soil column.  Manually compact the soil within the pipe and fill with 18" or more of water.  Measure the rate of decline in the pipe and adjust application rate for your soils as needed.  45 lb pails of sodium bentonite are available for testing application rates or treating small areas.

Free Standard Freight shipping to lower 48 states.

Lift gate service is unavailable for 3,000 lb sacks- Unloading equipment needed at delivery site. If lift gate is required, 2,000 lb bulk sacks are available.

Allow 7-10 days for freight carrier delivery.

Bentonite Specifications

Granular Bentonite particle size = -8 Mesh

All bentonite particles will pass through a 0.0937" opening. As with any "minus mesh" screened product, all particles are smaller than the mesh opening. This results in a gradient of particle sizes from the 0.0937" to finer powder that is ideal for blending with soil and compacting. 

• Bentonite Swell Index = 30
• Bentonite Percent Moisture = 16.6%
• Aged Fann 600 = 34.0 (measure of viscosity)
• pH = 7.75

Bulk Bentonite Clay Reviews - What our Customers are Saying