Pond Sealer: How to Seal a Pond Naturally (Best Products & Methods)
by Tory Jon | Last Updated: October 29, 2026
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If you've confirmed your pond leaks due to a hole or crack in the liner or foundation…
It's time to seal that baby!
Match the repair to the surface: use a compatible patch or sealant for a flexible liner, a prepared coating system for concrete, and soil-based sealing methods for an earthen pond.
Let's look at the best pond sealer products on the market today and help you find the right choice for your unique pond.
What Is Pond Sealer
Pond sealer is a product used to fix small holes and cracks in the foundation of your pond.
Important
Locate the water loss before buying a sealer. A low liner edge, leaking hose, waterfall splash, and a hole in the pond base need different repairs. If water loss exposes fish or leaves a pump running dry, address that immediate problem while locating the leak.
The type of pond sealer you'll use depends on a few factors:
- The type of foundation your pond has, whether a pond liner, concrete foundation, or natural soil/clay foundation.
- The size of the hole or crack
- Whether you can/want to drain your pond to repair the hole
Important
Is your pond really leaking? Ponds naturally lose water due to evaporation, especially in warmer climates. To find out if you have a leak and exactly where that leak is, check out our guide on How To Find A Leak In A Pond In 2 Simple Steps.
Once you've identified where the leak is in your pond, it's time to seal it!
But first, here is a quick comparison of the top pond leak sealers we'll be covering below and the type of pond they are used for.
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Best Pond Sealant Comparison Chart
How To Stop A Pond From Leaking
The sealant you'll need to stop your pond from leaking depends on the type of pond foundation you have. We have them broken out by pond liner (a liner sheet usually made of rubber or PVC), concrete foundation, or a natural soil/clay foundation. Skip to the section that best describes your pond for specific instructions on how to stop your pond leak using the recommended product.
Pond Liner Sealant
If you have a hole or tear in your pond's liner, you have a few options to repair it. One involves draining your pond, and one doesn't.
Important
Judge a liner repair by the material, condition, location, and extent of damage. A single tear in sound liner may be patchable, while brittle material or widespread damage may favor replacement. Check the repair-system instructions and our pond liner guide before deciding.
Underwater Pond Liner Sealant
Gold Label Underwater Sealant is an effective way to seal tears in your pond liner without draining your pond's water.
This product uses moisture as a curing agent, making it ideal for underwater sealing. And it's safe for koi and other fish ponds, as well.
Confirm compatibility with your exact liner material and clean away algae before applying the sealant. Gold Label's instructions call for a bead with enough thickness to cure; pressing it completely flat can spoil the seal. Larger tears need a compatible liner patch rather than a thin smear over the gap.
Application
- Step 1: Clean the surface of the pond liner around the tear.
- Step 2: Follow the product's hole-size and patch instructions. Gold Label permits sealant alone for a small hole or split no larger than 10 mm; larger damage needs a suitable patch.
- Step 3: Follow the curing and refilling instructions for the repair location and temperature. Keep the required sealant thickness beneath a patch.
Pond Liner Patch Kit
The Cofair Tite Seal Pond Liner Repair Kit shown below is a patch-kit option. Check the exact kit against your liner material before buying; use its specified preparation, primer, overlap, and curing method.
Choose a patch kit explicitly compatible with your liner. EPDM, PVC, polyethylene, and polypropylene can need different bonding methods. Check whether the kit needs a dry surface, primer, or a particular overlap around the damage.
Keep in mind that you will need to drain your pond water to at least a few inches below the tear to install the patch. If that's not an issue, I would recommend using the patch kit over the underwater sealant as it tends to work better in our experience and is one of the cheapest ways to seal a pond liner.
Application
- Step 1: Lower the water only as far as the repair needs. Keep enough well-aerated water for any fish left in the pond; use suitable aerated temporary housing if the remaining water cannot support them. Before refilling, remove chlorine or chloramine from replacement water with a conditioner labeled for the disinfectant present. Return housed fish only after required curing and suitable water conditions. Just be sure to drain it so the surface of your pond's water is at least a few inches below the tear. This will allow you enough room to apply the patch. Be sure to follow our guide on how to drain a pond quickly and easily.
- Step 2: Clean the surrounding area of the tear with the included solvent wipes
- Step 3: Using the dry scrub sponge, scrub and dry the damaged area.
- Step 4: Remove the backing paper from the patch and apply over the tear.
- Step 5: Use the seam roller to apply pressure to the patch and ensure a tight bond.
Concrete Pond Sealer
Concrete ponds, while very durable, will start to form cracks over time. This is especially true if you live in an area that has extreme temperatures.
Sealing a concrete or cement pond is different from sealing a pond liner. So, how do you seal a concrete pond that leaks?
One of the best products to seal a concrete pond is an epoxy pond sealant paint like Pond Armor!
Pond Armor Pond Sealant
Pond Armor Pond Shield is an epoxy coating for properly prepared surfaces. Repair cracks and unstable material before coating. Its application guide calls for a clean, completely dry, structurally sound surface and suitable crack repairs.
The coating is intended for service under water after correct application and curing. Apply it to the prepared dry surface, let it cure, and inspect it before filling the pond or returning fish.
And it's available in many different colors including clear, black, competition blue, gray, green, tan, white and sky blue.
Application
- Step 1: Drain and dry the work area, repair cracks, and prepare the surface according to the manufacturer's directions.
- Step 2: Mix a small batch at the specified ratio and move it promptly into a flat tray. Mixed epoxy can become very hot if left in the mixing cup.
- Step 3: Apply the specified coating thickness over the prepared surface.
- Step 4: Allow at least the stated curing time before use; temperature and project conditions can affect it.
- Step 5: Inspect for pinholes, thin spots, and missed areas. Correct defects and allow repairs to cure before adding water.
Check out Pond Shield's tutorial on concrete crack repair for ponds.
Soil & Clay Pond Sealer
If you have a natural soil or clay pond foundation, common with many farm ponds, then the two most popular options are polymer pond sealers and bentonite sealers.
Polymer Pond Sealer
Soilfloc Pond Sealant and Damit Pond Sealer are two of the most popular polymer-based pond sealers today.
Polymer sealers are intended for particular seepage conditions in earthen ponds. Product chemistry and application methods vary. Check the manufacturer's requirements for soil, water chemistry, vegetation, and leak type before buying; a failed pipe or damaged embankment may need physical repair.
Check the instructions for the specific product before treating a pond with fish. DamIt Rapid Leak Sealer is not recommended for small fish ponds, ornamental ponds, or shallow water. Its manufacturer also warns that treatment can reduce oxygen and calls for staged application where fish are present. Do not assume another polymer sealer has the same restrictions or application method.
Application
- Step 1: Broadcast the powder evenly over the surface of your pond. Follow the product's application instructions for your pond. DamIt's manufacturer recommends spreading the dry powder over calm water and warns that treated surfaces become very slippery; avoid walking through applied polymer. If using Soilfloc, you'll have two powders to evenly spread across your pond (Damit is just one powder). Be sure to use the recommended amount of powder as described on the product package.
Follow the product's site-preparation requirements. General application considerations include:
- Don't apply powder on windy days. You want the water to be as calm as possible.
- Use a fertilizer spreader or hand scoop to evenly spread out the powder during the application process.
- Be sure to remove any heavy vegetation prior to application so they don't impede the ability of the polymers to enter the cracks.
Bentonite Pond Sealer
If you're looking for how to seal a pond naturally, then look no further!
Sodium bentonite is a clay that swells when wet and can reduce seepage through suitable pond soils. Its success depends on the soil and installation, so check the site before choosing an application rate.
While you can sprinkle bentonite clay over the surface of the water, it's most effective when your pond is drained and it's applied directly to the foundation.
Application
There are a few different application techniques for pond sealing with bentonite clay, with the most popular being the blanket method:
- Step 1: Move fish to suitable aerated temporary housing before draining a stocked pond. Drain the pond and clear the foundation of vegetation and debris.
- Step 2: Prepare the exposed pond basin and set aside suitable cover soil for the selected installation method.
- Step 3: Repair erosion channels and other defects before applying a continuous seal; determine the soil treatment from the site conditions.
- Step 4: After all holes are covered, a layer of bentonite clay should be applied evenly over the entire foundation.
- Step 5: Cover and compact the treated layer according to the chosen installation plan. Protect it from drying and damage before refilling.
- Step 6: Refill gently without disturbing the seal. Treat replacement water for chlorine or chloramine before fish are exposed. Return fish only after any required curing and when temperature and water quality are suitable.
So, how much bentonite does it take to seal a pond? The answer depends on the type of soil(s) your ponds foundation is made up of.
Choose the application rate from the soil and installation plan. Test the soil and follow a suitable installation plan. Bentonite needs contact with the leaking soil and proper compaction; simply adding more clay over rock or gravel may leave the leak unresolved. Kansas State's guidance on leaking farm ponds describes soil preparation and compaction methods.
Natural Waterscapes Granular Sodium Bentonite Clay is intended for sealing soil-bottom ponds. Its application guidance calls for incorporation into the pond soil followed by compaction, or a confined blanket under cover soil. Select the amount for the soil and method; it is not a repair for a torn synthetic liner.
Pond Waterfall Sealer
A common but often overlooked source for pond leaks is in and around the waterfall.
TotalPond Waterfall Pond Foam Sealant
TotalPond Waterfall Foam sealant is simply a polyurethane foam used to fill, seal, and bond rocks that are used for waterfalls.
The foam expands between rocks to guide water over the waterfall. Keep a sound liner beneath the rocks and repair any liner puncture separately. TotalPond describes the foam's purpose as filling gaps for better flow over rocks.
Follow the curing instructions before running water over the foam. Wear protective glasses, nitrile gloves, and protective clothing during application, and keep ignition sources away while dispensing.
Application
- Step 1: Shake the foam sealant can well and screw on the nozzle adapter.
- Step 2: Test on an experimental surface to make sure foam sticks.
- Step 3: Fill in any gaps, cracks, or crevices about 1/3 of the way to allow for expansion.
- Step 4: Allow 12 to 24 hours to fully cure.
*Important: Follow the manufacturer's directions on the packaging for the most up-to-date information when using any pond sealant product.
Sources
- Hutton Aquatic Products: Gold Label sealant FAQs
- Pond Armor: Pond Shield quick start
- Kansas State University Extension: Leaking farm ponds
- TotalPond: Waterfall foam sealant
- Shalex Industries: DamIt dam sealer FAQs
- Shalex Industries: Dam Sealer application guide
- Natural Waterscapes: Granular Bentonite Clay for Pond Sealing
- CDC: Water Disinfection with Chlorine and Chloramine
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