If you notice your concrete pond is losing water, the concrete might have a crack in it. Concrete is susceptible to weather conditions and can form cracks due to frost and thawing in winter, an earthquake, or when the ground settles beneath your pond. You can repair cracks yourself.
Step 1 - Remove Flora and Fauna
If you can, try to remove the fish and plants from your pond and store them in a large watertight container while you repair the concrete.
Step 2 - Drain the Pond
Drain all the water from your pond using an electric pump. If you don’t have a pump, siphon the water through a garden hose. Remove any remaining plants and fish. Note it can sometimes be easier to remove them as the pond is draining.
Step 3 - Visual Inspection
Once your pond is completely drained, inspect it thoroughly. Large cracks are easy to spot, so look out for smaller or hairline cracks.
If your crack is very big and deep, you might need to consider replacing your pond. If this isn’t the case then continue with these steps.
Step 4 - Prepare the Crack
If the crack you spotted is a hairline crack, you will need to widen it. This will ensure the sealant can penetrate to an acceptable depth in order to provide a longer lasting concrete repair to your garden pond.
To widen the crack, use a hammer and chisel, but do not apply to much pressure as you don’t want to make the crack too big.
Step 5 - Clean and Dry
Use a stiff wire brush to clean the crack and the surrounding area, making sure any plant debris is thoroughly removed. When clean, dry the crack and the surrounding area.
Step 6 - Repair Materials
The best material for repairing your concrete pond is more concrete, though you can purchase specialist pond sealants from garden centers. The one you need will depend on the size and depth of your crack.
If you use concrete, use a trowel to fill the crack. Try to make sure you don’t leave any gaps.
Step 7 - Finishing Touches
When the concrete has dried, sand the area to smooth the surface. Use multiple sandpaper grits to get a smoother and smoother finish. For added protection, you can coat your garden pond with a layer or two of pond paint.
WARNING: Wear safety equipment to protect your eyes, mouth and hands from concrete particles generated by sanding.