Pond Sealer: How to Seal a Pond Naturally (Best Products & Methods)
by Tory Jon | Last Updated: March 25, 2022
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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!
But, what kind of pond sealer should you use for best results?
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
It's good practice to seal any holes or cracks in your pond as quickly as possible. Besides the obvious issues with water loss and fish health, cracks in your foundation will only worsen if you don't repair them in a timely manner.
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.
Best Pond Sealant Comparison Chart
*Buying through links in this chart may earn us a commission at no additional cost to you.
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
If the tear is longer than 5", I recommend replacing the liner completely. Check out our Pond Liner guide to find the best liner for your pond or water garden.
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.
This pond liner sealant works on all types of liners, including rubber, PVC, EPDM, plastic, and more.
Application
- Step 1: Clean the surface of the pond liner around the tear.
- Step 2: Apply the underwater sealant directly to the tear.
- Step 3: Allow the sealant to cure for at least 24 hours
Pond Liner Patch Kit
Pond liner patch kits effectively repair tears and holes in all different types of liners, including EPDM, PVC, polyethylene, and polypropylene liners.
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: Drain your pond. You don't have to completely drain the entire pond. 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 is a non-toxic epoxy designed to waterproof and prevent cracks and holes from forming in concrete, cement, wood, brick, and many other types of ponds. And it can be used to repair small cracks by essentially gluing the cracked foundation back together.
This liquid pond sealer is designed for underwater use and is a plant and fish safe pond sealant.
And it's available in many different colors including clear, black, competition blue, gray, green, tan, white and sky blue.
Application
- Step 1: Prepare the surface according to the manufacturer's directions.
- Step 2: Mix the sealer with the hardener. Only mix enough that you can use within 30 minutes.
- Step 3: Apply the sealer to the damaged area.
- Step 4: Let dry. Typically takes around 24 hours to fully cure.
- Step 5: Inspect the area and touch up as needed.
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.
A polymer sealer is just a powder that you sprinkle onto the surface of your pond. The powder has a positive charge that draws it to the bottom of your pond and eventually is drawn into the cracks in your pond's foundation. Once in the cracks, the powder will expand and plug the crack, effectively stopping the seepage.
Both Soilfloc and Damit are non-toxic and safe for humans, fish, and other aquatic life.
Application
- Step 1: Broadcast the powder evenly over the surface of your pond. You can do this from a boat (in larger lakes or ponds), or in shallower ponds, you can walk very slowly through the water. 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.
And that's it! For best results:
- 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.
- If you are applying the powder while walking through your pond, be sure to broadcast it out behind you (not in front of you).
Bentonite Pond Sealer
If you're looking for how to seal a pond naturally, then look no further!
Bentonite clay pond sealer is essentially a natural clay that expands up to 15 times when exposed to water to create an effective seal in the cracks of your pond or lake.
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: Drain your pond and clear the foundation of any vegetation and debris.
- Step 2: Remove the top 5 inches of soil from your water bed and set it to the side.
- Step 3: Fill in any holes, cracks, or gaps with a mixture of bentonite and soil (one part bentonite and five parts soil).
- Step 4: After all holes are covered, a layer of bentonite clay should be applied evenly over the entire foundation.
- Step 5: Replace the 5 inches of soil we removed in step 2.
- Step 6: Refill the pond with water.
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.
| Type of Soil | Sealant Amount |
|---|---|
| Clay | 1 - 1.5 lbs. per sq. ft |
| Sandy/Clay Mix | 2 - 2.5 lbs. per sq. ft |
| Sand | 3 - 4 lbs. per sq. ft |
| Rock or Gravel | 5 - 6 lbs. per sq. ft |
Always refer to the manufacturer's recommended amounts when applying bentonite clay.
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.
This moisture-cured sealant expands 2 to 3 times to effectively fill any gaps or cracks to prevent leakage.
It's also safe for fish and aquatic plants.
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.
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