In order to make sure that the water feature stays waterproof once coated, any cracks in the surface need to be repaired properly. Many different methods can be used to fix these problems, but for the average crack, making sure it is filled with Pond Shield epoxy and then dressed with fiberglass being used in conjunction with Pond Shield will ultimately make the fix very durable.
After cutting, make sure that the crack has been thoroughly cleaned and etched. Use a vacuum to remove any loose debris. You can also use an air compressor to blow debris out of the crack prior to coating.
The concrete needs to be essentially glued back together. The best way to get the coating down into the crack is to cut straight down into it with a concrete cutting wheel. The cut does not have to be too deep, but it does have to be straight down and not angled. This way the epoxy coating is able to attach to a direct vertical surface where the sheer strength is increased as opposed to when the cut is angled like a “V”.
For more ways for fixing cracks in a pond, see: