Sealing A Leaky Dam With Bentonite: Step-By-Step Guide

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Last updated: April 2026 | Author: Angus Hughson, Big Ditch Dam Building Company

Bentonite needs to be applied in a very precise way to ensure it works effectively and permanently

The optimal result of using bentonite to seal a dam properly is achieved when the walls and base need to be 6-way cross ripped down to 600mm

Then the Bentonite has to be spread over all areas requiring sealing at a rate of 30kgs per sqm

Then the Bentonite needs to be ripped as per step one to get it integrated into the dam wall & base clay

Then the ripped area needs to be final trimmed and smoothed with a mud bucket

Then the whole area that has had Bentonite applied to it has to be compacted with at least 6 passes on each square meter.

You can use an excavator for compaction. A pad foot roller is not required.

Then the dam needs to be filled slowly to allow the Bentonite to expand 400 times its original molecular size

This swelling is what creates the permanent seal

Important things to note when using bentonite to seal a dam properly

The Bentonite must be integrated into the clay.

If you just apply Bentonite to seal a dam on the surface, when it swells, it has no voids to fill and will be a waste of your money

Measure the dam – width x length x depth – this will give you the total square meters.

Multiply this number by 30 – and this is the amount of Bentonite required to seal your dam in kilograms

We sell Bentonite to seal a dam, and we call also apply it for you.

Contact us for a free quote

Frequently Asked Questions