Key Points

• Fix a leaking concrete pond by sealing hairline cracks with pond-safe epoxy, patching larger cracks with hydraulic cement, or resurfacing the entire pond with waterproof epoxy.
• For long-term reliability, replace concrete with a flexible 45-mil EPDM pond liner that stretches with soil movement, resists cracking, and provides decades of leak protection.
• Prevent future pond leaks by maintaining consistent water levels, avoiding complete draining, managing nearby plant roots, and inspecting surfaces regularly for early signs of damage.

Cracked Up Over Concrete? Here’s the Fix That Lasts

Noticed your concrete pond losing water and wondering if it’s a small crack—or something bigger?

Trying to figure out whether you should patch it, seal it, or just start over?

In this post, you’ll learn how to identify the source of your concrete pond leak, what tools and repair methods work best for different crack sizes, and when it’s smarter to install a flexible liner instead of fighting the concrete.

By the end, you’ll know how to stop the leak and prevent future problems without wasting time or money on pond repairs that don’t hold up.

Call California Aqua Pros or fill out our contact form to talk through your options—we’ve helped hundreds of homeowners do it right the first time.

How Do You Fix a Leaking Concrete Pond?

A leaking concrete pond can be repaired using a few different methods depending on the severity and location of the issue.

Minor hairline cracks may only need surface sealant, while deeper structural damage may require cutting, patching, and full resurfacing.

In some cases, the best solution is to install a flexible pond liner over the existing concrete to permanently seal leaks and avoid recurring issues.

California Aqua Pros does not install concrete liners for ponds.

Concrete ponds tend to crack unless they’re built like full-scale pools—with excavation, steel rebar, gunite application, and professional surfacing—which is extremely expensive.

Our preferred method uses a 45 mil EPDM pond liner that flexes with the ground and holds water reliably for years.

Follow the link to learn more about our views concerning flexible rubber liners vs. concrete.

Fixing Hairline Cracks

Hairline cracks in a concrete pond often appear near the pond bottom or along the walls and can be sealed with minimal prep.

Start by cleaning the area with a pressure wash and scrubbing the crack using a wire brush to remove algae, dirt, and loose debris.

After drying the surface, inject a pond-safe epoxy into the crack and follow with a surface coating epoxy to reinforce the repair.

These types of repairs are best for localized pond leak issues where the rest of the structure remains solid and dry.

Avoid using standard concrete patching products unless they are designed for constant water exposure.

Repairing Larger Cracks or Structural Damage

For wider or deeper cracks, a more aggressive crack repair approach is needed.

First, cut open the crack using a grinder to form a V-shaped channel, which will help new materials bond properly.

If the damage extends deep into the structure, consider embedding mesh or small rebar rods for added strength.

Next, apply hydraulic cement or epoxy mortar to fill the void, pressing it firmly into the affected area.

Once hardened, finish the pond repair by applying a waterproof coating across the entire surface of the patch.

Be sure to monitor for new cracks in the surrounding area, which may suggest more serious structural movement or water pressure imbalance.

Resurfacing the Entire Pond Interior

If the concrete surface is riddled with microcracks or shows signs of widespread seepage, a full resurfacing may be needed.

Begin by acid-etching or cleaning the surface to remove any residue that might prevent adhesion.

Apply two coats of waterproof epoxy coating, allowing each coat to cure according to the manufacturer’s instructions.

Use brushes or rollers to evenly spread the material across the entire pond, aiming for at least 10 mils of total thickness.

Pay special attention to seams, edges, and corners, where water pressure tends to push hardest.

This method offers better protection than patching, but can be labor-intensive and expensive if you need to reapply in the future.

What Causes Concrete Ponds to Leak?

Understanding what caused your pond to crack or leak can help you avoid repeating the same problem after repairs and recognize the signs your backyard pond needs repairs.

Natural Ground Movement

Shifting soil is a common issue in backyard pond construction.

As the ground expands or contracts due to moisture levels, tree roots, or settling, the rigid structure of concrete can’t flex and may develop stress cracks.

Over time, these movements may cause separation at the joints or long diagonal cracks along the pond walls, leading to slow water loss or full leaks.

Freeze-Thaw Cycles and Moisture Shifts

Even though freeze-thaw conditions don’t typically happen in the East Bay area, inconsistent exposure to moisture can still weaken the surface.

If the pond is drained and left exposed to the sun and evaporation, the concrete can shrink and fracture.

This is especially problematic in older concrete ponds that weren’t properly cured or sealed from the start.

Poor Original Construction

Some concrete ponds are built with insufficient rebar, thin walls, or improper concrete mixtures.

Without additives to resist water absorption or structural reinforcement to prevent cracking, these ponds are more likely to leak within just a few years of installation.

Diagnosing the Leak Before You Repair

Before you begin applying coatings or crack filler, it’s essential to locate the leaking area accurately.

This will help you choose the right pond repair method and avoid treating the wrong spot.

Isolate the Source

Turn off the pump and let the pond sit for at least 24 hours.

If the water level stops dropping at a certain point, it likely means the pond leak is near that level.

If the water level drops all the way to the pond bottom, it may be a liner or base issue.

Mark Water Loss

Use painter’s tape or a grease pencil to mark the water level and check it every few hours.

A consistent drop in water level helps identify how fast the pond is leaking and whether it’s a small crack or a major hole.

Look for Cracks and Seepage

Walk around the pond and inspect the concrete surface for visible cracks, wet spots in the surrounding soil, or areas where plants or rocks look unusually damp.

If you notice any erosion or water stains below the edge of the pond, this may signal ongoing seepage.

Tools and Materials You May Need

Before starting any pond repair, gather the right tools and materials to avoid mid-project delays.

The tools you’ll need vary based on whether you’re fixing cracks, resurfacing, or installing a new liner.

For Crack Repairs and Patchwork

• Wire brush for cleaning the concrete surface
• Grinder with a diamond blade to open cracks
• Hydraulic cement or pond-safe epoxy
• Trowel or putty knife for application
• Mixing buckets
• Gloves and safety goggles
• Pressure washer for cleaning the entire pond beforehand

For Full Pond Coatings

• Pond-friendly epoxy or similar waterproof coating
• Rollers and brushes for even coating
• Respirator mask for fumes
• Primer if required by the product
• Second coat material for additional waterproofing
• Measuring tools to track thickness of coating

For Installing a Pond Liner Over Concrete

• Flexible pond liner (EPDM, 45 mil preferred)
• Underlayment fabric to protect the liner
• Scissors or utility knife
• Liner seam tape or adhesive
• Landscaping fabric staples or pond edge blocks
• Hose or pump to refill once installed

California Aqua Pros exclusively uses EPDM liners because they stretch, flex with the ground, and provide long-lasting waterproof performance without cracking like concrete.

Alternative Options if Repairs Don’t Hold

Sometimes, even after applying patchwork or resurfacing, the pond continues to leak or develop new issues.

If you’re tired of chasing the same problem, consider these long-term solutions.

Installing a Pond Liner Over the Concrete

Instead of breaking out the entire structure, you can retrofit the existing shell with a pond liner.

A properly installed liner isolates the water from the concrete, eliminating ongoing seepage.

This method is especially useful if the concrete pond has too many small cracks to seal individually.

Ensure the liner extends over the top edge of the pond to prevent leaks from behind.

Just make sure you know how deep a fish pond should be before embarking on this repair.

Rebuilding with a New Liner-Based System

If the structure is badly damaged, it may be more cost-effective to demolish and rebuild using a liner-based method.

This approach involves reshaping the pond with soil, placing a thick underlayment, and installing a durable EPDM pond liner designed to last 20–30 years.

A liner system also allows for more creative pond designs, better fish habitat, and easier integration of features like waterfalls, rocks, or aquatic plants.

Tips to Prevent Future Leaks in Concrete Ponds

Once you’ve completed a pond repair, take preventive steps to extend the life of your pond and avoid having to fix the same issues again.

Maintain Consistent Water Levels

Letting the water level drop below certain cracks can allow drying and shrinkage.

If the water level drops too often, check for evaporation, wildlife interference, or pump issues.

Avoid Draining the Pond Completely

Sudden draining can create pressure imbalances that push from the outside in, especially if the surrounding soil is wet.

This pressure can worsen existing cracks or cause new ones to form.

Keep Plants and Roots in Check

Invasive roots from nearby plants can force their way through weakened edges and corners.

Maintain a buffer zone around the pond or use a root barrier if planting nearby.

Don’t Skip Routine Inspections

Check for signs of moisture loss, algae buildup near seams, or visible cracks every few months.

Early detection makes repairing cracks simpler and reduces pond repair costs over time.

When to Call a Professional

If you’ve tried patching your pond and it still won’t hold water, or if you’re dealing with structural damage across the entire surface, it’s time to consult a pro.

Concrete pond repairs are labor-intensive and require knowledge of how materials behave under constant water pressure.

Misapplied coatings or cheap fillers will fail quickly and waste money.

California Aqua Pros offers pond repair services starting at $299 plus labor and materials.

Our team can inspect your leaking pond, identify whether patching, resurfacing, or full liner replacement is best, and give you a lasting solution.

FAQs About Leaking Concrete Ponds

What should I do if my repair sealant fails after a few months?

If the sealant peels or bubbles, it’s often due to poor surface preparation.

Clean the area thoroughly, let it fully dry, and roughen the surface before reapplying sealant to ensure better adhesion.

Can I use hydraulic cement underwater or on a damp surface?

Yes, hydraulic cement is designed to set quickly, even on wet concrete.

It’s best used in urgent or high-moisture situations, but treat it as a temporary fix unless combined with proper structural repairs.

Are there natural or low-cost alternatives for small leaks?

Bentonite clay can be used for small leaks, especially on the pond perimeter.

It forms a natural, watertight seal when compacted and is a good, eco-friendly solution, though it might not last as long as synthetic options.

Turn Pond Leaks Into Peace of Mind With California Aqua Pros

Cracks and leaks don’t have to mean the end of your backyard water feature.

Whether you’re sealing a small leak or considering a full liner retrofit, the right materials and approach can restore your East Bay pond’s beauty and function.

Let the pond experts at California Aqua Pros help you fix your leaking concrete pond the right way—from durable EPDM liners to weekly maintenance and full pond remodels.

Reach out today to request an on-site consultation and get your water feature back in working order.