How to Repair a Leaky Concrete Pond

Written by cullend
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How to Repair a Leaky Concrete Pond
Ponds can develop leaks. (pond image by mtooner from

By virtue of their purpose, ponds must be able to hold water to sustain a biologically diverse ecosystem for plants, fish, birds and aquatic animals to thrive. However, it is not uncommon for concrete ponds to develop cracks over time and slowly leak water into the soil below. It is imperative that the leak is repaired as soon as possible as water can exacerbate the problem. Follow these steps to stop and prevent future leaks.

Skill level:

Things you need

  • Seine
  • Dip net
  • Holding tank
  • Water pump
  • Pond liner
  • Utility knife
  • Decorative stonework
  • Bentonite-based pond sealant
  • Cup
  • Granular spreader

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  1. 1

    Remove all fish and aquatic life you wish to repopulate with a seine and/or dip net, depending on the size of the pond. Keep them in a holding tank until repairs are complete and they can be re-acclimated to the pond. Drain the pond using a submersible or in-line water pump. Remove all organic material from the pond basin so you have a smooth surface on which to install the liner.

  2. 2

    Install the pond liner by laying it in the bottom of the pond. If the pond has a bottom drain, cut a hole in the bottom of the liner to expose the drain. The liner should lay over the edges of the pond by at least 1 foot. Lay down decorative stones to hold the liner in place. At this time, you might also add some fish structure in the pond by stacking several stones on top of one another.

    How to Repair a Leaky Concrete Pond
    Fish enjoy structure. (fish image by Henryk Olszewski from
  3. 3

    Spread a layer of Bentonite-based pond sealant over the pond liner for an extra tough seal. Apply between 1/4- to 3/4-inch thickness evenly distributed throughout the pond. Use a cup or granular spreader to achieve the proper layering.

  4. 4

    Refill the pond with the submersible or in-line pump. As the water comes in contact with the Bentonite-based sealant, the individual granules will form a cohesive mat, completely sealing the bottom of the pond.

  5. 5

    Restock the pond with the fish and other aquatic animals from the holding tank.

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