Sodium bentonite clay can be used as an effective and all natural pond sealer. The bentonite clay is sold as a fine powder, that when mixed with water will expand 15 to 18 times its original size. Once it hardens, it forms a strong sealant, making it an excellent method for sealing a pond. In addition to being able to seal a pond with bentonite, it can be used to repair an existing pond leak.
What You Will Need:
Sodium bentonite clay
Step 1: Determine how much bentonite clay is needed to seal your pond. The amount of bentonite clay will depend both on the size of the pond as well as the type of soil. More bentonite will be needed to seal course soils than fine soils. Typically, about one pound per square foot should suffice.
Step 2: Using a shovel, dig the top four to six inches of soil from the entire interior of the pond. Set the soil aside, as it will be used later.
Step 3: Identify any holes in the pond and fill them with a mixture of 1 part bentonite clay and 5 parts soil.
Step 4: Using a lawn roller, smooth out all areas of the pond until evenly packed.
Step 5: Cover the entire pond with a layer of bentonite clay.
Step 6: Cover the bentonite clay with the previously dug up soil, so that all the bentonite clay is evenly covered with four to six inches of dirt. Be careful during this process so as not to move the bentonite clay around.
Step 7: Using your lawn roller, compact all of the topsoil.
Step 8: Add a layer of gravel about one inch deep, covering the entire pond.
Step 9: Using a hose, wet the entire area of the pond, but don’t fill it just yet. Ensure that all of the pond walls are well soaked enough so that the water seeps down to the layer of bentonite.
Step 10: Wait at least 48 hours for the bentonite to fully expand before filling your pond.
– If the pond has already been filled with water, then bentonite clay can also be sprinkled on the surface of the water and allowed to settle. This method isn’t as effective as applying bentonite clay directly to the soil. However, for sealing leaks in an existing pond where draining the existing water is difficult, this would be the preferable method.