how to seal a pond

how to seal a pond

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Ponds are beautiful additions to your garden, and what is more, is that they are also amazing diverse ecosystems so it’s not hard to see why they are so popular.

Unfortunately, sometimes your ponds can leak due to a crack or a hole in the pond’s liner or the pond’s foundations. 

Nobody wants their pond to leak so if you’ve confirmed that you’ve got this issue, let me help you seal it right on up and take all your troubles away.

Sometimes, it can be difficult to know where to start, what pond sealer should you be using anyway?

There’s quite a saturated market so differentiating the effective products from the bad can be quite difficult, which is what I’m here for. 

Together, let’s go through the best products and methods available and find the perfect solution for your specific pond. 

What Is Pond Sealer

If you do see a crack in your pond, seal it up as soon as possible because while it may only seem like a small crack at the moment, it will only get worse as time goes on and small cracks can develop into large holes.

These cracks and holes are also going to cause you to lose water and may impact the health of any fish in the pond. 

So what is a pond sealer?  You use a pond sealer to fix the small cracks and holes that you find in the foundation of your pond.

There are several different kinds of pond sealers on the market and which one you use will depend on several different factors; the type of pond you have, the type of foundation you have, the size of the crack/hole you’re filling, and whether you are draining the pond to repair the crack. 

How To Seal A Leaking Pond

So, as I just mentioned, which pond sealer you use will change based on the foundation of your pond. Generally, there are three main categories that you can fall under: 

  • Pond Liner (Liner sheets are often made of PVC or rubber)
  • Concrete Foundations
  • Soil/Clay Foundations 

In each of these categories, I’ll go over the best products to use and how to use them so that no matter what type of pond you have, we can make sure it gets sealed. 

Pond Liner Sealants 

If you’ve identified a tear or a hole in the liner of your pond you’ve got two options. One option will mean you have to drain your pond first, and the other keeps the water where it is. 

Which option you pick is your decision, however, your pond water has loads of micro-organisms and healthy bacteria that create a highly diverse ecosystem in your pond, and draining your bond means you will lose that and have to start again.

So where possible I would advise not draining your pond unless absolutely necessary. 

Underwater Pond Liner Sealant

If you’re looking for a sealant that you can use underwater I would really recommend Gold Label Underwater Sealant. 

I would say that this sealant is mid-range-expensive in price but considering it saves you the hassle of having to drain your pond, it is certainly worth the little extra you’ll spend. 

Moisture is used as the curing agent in this product which makes it perfect for sealing your pond underwater.  Great news for fish lovers, this product is also fish-friendly.

Whether your liner is made with rubber, EPDM, PVC, or plastic this solvent will work for you. So let’s get into how to use it!

Application

The application of this product is really easy, just follow these 3 simple steps. 

  1. Clean the pond liner around the affected area. 
  2. Apply the sealant to the tear.
  3. Leave to sure for a minimum of 24 hours. 

Pond Liner Patch Kit

This pond liner patch kit can also combat a fair few different types of liners including PVC, EPDM, polyethylene, as well as polypropylene. So it’s safe to say it’s a great universal option, no matter what kind of liner you have. 

This sits nicely in the cheap – midrange in price and so is a better option of the two if you’re shopping on a budget.

I like this kit because it’s really effective. You can be sure that this will do the job at hand. For this product, you are required to drain your pond.

How much of your pond you’ll need to drain will really depend on where the tear or hole is in your liner. The pond needs to be a good few inches below your tear so that you can patch it up. 

If you really want to make sure that your pond is reliably sealed, use the patch kit over the underwater sealant for a firm and strong hold. 

Application

The patch kit is a slightly more difficult procedure than the one above but can still be done in just five steps. 

  1. Drain your pond approximately 2-3 inches below the tear. 
  2. Clean the affected area with the wipes included in the kit. 
  3. Scrub and dry the affected area with a dry scrub sponge.
  4. Discard the backing paper of the patch, and then apply the patch over the tear.
  5. Use a seam roller, applying pressure to the patch to create a tight bond. 

Concrete Pond Sealers

Even concrete ponds which are arguable the most durable foundation for your pond will form cracks after a certain amount of time.

If you live somewhere that experiences extreme temperatures this will only increase the chances of these cracks developing over time. 

If you’re looking for a sealant for your pond, I honestly couldn’t recommend Pond Armor 

Pond Sealant enough. It is an epoxy pond paint sealant and it’s without a doubt the best on the market.  

Pond Armor Pond Sealant 

Pond Armor will not only waterproof your pond but prevent any holes or cracks from forming. It can be used on concrete, cement, wood, brick, and many other materials. It essentially works like glue and sticks the cracks you have back together. 

Now, this does veer more towards the expensive side of the price scale, but it’s such a high quality and reliable product so it will be worth every penny that you spend. 

It’s a great choice for your ecosystems too as it is non-toxic, can be used underwater so you don’t need to drain your pond, and is both plant and fish-friendly (see lights). 

And if aesthetics are important to you, it also comes in an array of colors such as clear, black, blue, gray, tan, and white so no matter what color your pool there should be a shade that works for you. 

Application

Another thing to love about Pond Armor is how easy it is to use. Follow these simple steps to have a sealed pond in no time. 

  1. Following the manufacturer’s instructions, prepare and clean the surface. 
  2. Mix the sealer and the hardener. Do not mix it all in one go. 
  3. Apply the sealer to the affected area. 
  4. Leave it to cure for a minimum of 24 hours. 
  5. Inspect and repeat the process if needed. 

Soil And Clay Pond Sealers

Soil and clay ponds are often found on farms. If you have one of these types of ponds there are two main choices for sealing your pond.

There are polymer or bentonite sealers. Both work pretty well for your pond, so let’s have a look at them both in a little more detail. 

Polymer Pond Sealer

Polymer pond sealer is quite different from the other sealers that we’ve spoken about. This type of sealant is a powder that you’ll sprinkle into your pool.

The positive charge that comes from the powder draws it straight to the bottom of the pond until it is drawn into the cracks in the pond.

When this powder is in the cracks in your pond, it then begins to expand and thus fill in the crack and stop the leak. 

The best polymer filler that you’ll find on the market is Soilfloc Pond Sealant and Damit Pond Sealer, both of which are non-toxic, safe for humans, and fish-friendly. 

Application

This is probably the easiest sealant to use as it requires just one step.

  1. Spread the powder (one for Damit, two for Soilfloc) evenly over the pond. If the pond is large you can do this on a boat, otherwise, just spread the powder as you walk slowly through the pond. 
Tips And Tricks 

While there is only one step to this sealant there are few tips and tricks that will help it work more effectively so we’ll go over those now. 

  • Wait For Good Weather – You want a nice calm and clear day. If it’s windy the sealant won’t spread as effectively. 
  • Keep The Spread Even – I’d suggest using a scoop or a fertilizer spreader to make sure that you get an even coating over the entire pond. 
  • Keep The Pond Clear – If there is heavy vegetation in the pond, it will need to be removed to make sure that the powder can be pulled down into the cracks. 
  • Spread Behind Yourself – If you’re walking through your pond spread the powder behind you and not in front of you as you don’t want to be walking through the powder as you may disturb it. 

Bentonite Pond Sealers

Bentonite pond sealer is a great natural way to seal your pond. Bentonite clay is a type of clay that will expand up to 15 times its size when it reacts with water. This option is probably the most expensive option out there but it does work very effectively. 

Now, this can technically be spread over the water, but in all honesty, it works a lot better when your pond is drained and can be applied straight to the foundation. 

Application

There are several ways that you can seal a pond using bentonite clay, however, I’m going to go with the most popular option which is the blanket method. This is a little bit more complex than some other methods but is still fairly easy to follow.

  1. Drain the pond and clear it of any debris or vegetation. 
  2. Remove around 5 inches of soil from the water bed and place it to the side. 
  3. Fill in gaps, cracks, and holes with a mixture of soil and bentonite (five parts soil to one part bentonite)
  4. Apply a layer of bentonite clay over the entire foundation once the holes have been covered. 
  5. Replace the soil that was removed in step 2. 
  6. Refill your pond.

Always refer to your manufacturer’s recommendations for the amount of bentonite needed before you begin. 

Pond Waterfall Sealers

Now, this doesn’t exactly come under the liner, concrete, or soil and clay category but it is something to consider. I find that waterfall sealers tend to fall off the radar a little bit when actually they are a really great option.

If you’re going to use a waterfall sealer I would certainly recommend TotalPond’s Waterfall Pond Sealant Foam as your go-to choice. 

TotalPond Waterfall Pond Foam Sealant

This waterfall pond foam sealant is basically just a polyurethane foam that can fill, seal and bond rocks together.

It usually expands about two to three times its size to fill the hole and prevent a leak. It is fish and plant-friendly and is the cheapest option available. 

Application 

It’s nice and simple to use too, just follow these four steps. 

  1. Shake well and then screw on the nozzle adapter. 
  2. Spray a little on another surface and test that the foam is sticking. 
  3. Fill in the crack leaving about a third of the crack empty to allow for the foam to expand. 
  4. Leave for 12-24 hours. Repeat process if needed. 

Final Thoughts

None of the methods that we’ve discussed today should have seemed too complicated, hopefully, now you will be well on your way to sealing up that crack, gap, or hole that you’ve found in your pond. 

There are several different types of sealants and they can differ in price and ease so it is important to make sure that you have read over the different purposes of the sealants to pick the perfect one for your pond. 

I wish you the very best of luck, whether you’ll be wading waist-deep through your pond spreading sealant, or draining the pool to patch it back up, I hope that your pool is restored to its former beauty in no time at all. 

Photo of author

BY M. Kogan

Hello, I am Marcio. I am an architect and designer, alma mater is Mackenzie. Retired in theory, but an architect never retires completely. Along with architectural projects, I am a filmmaker and have completed some short documentaries. Filmmaking and design are my passions. In HomeQN I write about home decoration and foundations. The goal is to teach homeowners to DYI as much as possible, and when this is not possible, enable them through knowledge, to evaluate service quotations and choose the best service technicians.

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