How to Find a Leak in a Pond in 2 Simple Steps (and Quickly Repair It)

by Tory Jon | Last Updated: September 29, 2022

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Is My Pond Leaking?

This may seem like a silly thing to ask yourself if your pond is obviously losing water.

But what many don’t realize is that ponds naturally lose water due to evaporation. The amount of water it loses is largely dependent on climate conditions. High temperatures with lots of sunshine and low humidity will lead to a higher evaporation rate. Conversely, low temperatures with overcast conditions and high humidity will lead to a lower evaporation rate.

While you can get a close estimate of what your local evaporation rate is (FAO has a handy evaporation rate guide to help you figure this) it may be easier to check with local meteorological stations to see if they have that info. Even simpler yet, just keep in mind that in warmer climates it’s possible to lose a few inches of water a week to evaporation. So, if your water loss issue just started in the warmer months and you’re only losing a few inches a week, you may be fine.

This evaporation loss can still be annoying, however, so to keep water levels in check consider installing an auto-fill valve in your pond skimmer. This will ensure that your ponds water level will remain at the correct level without having to physically fill it yourself.

If you still suspect you have a leak in your pond, then read on.

How To Find A Pond Leak

While there are several areas in and around your pond you need to inspect for leaks, it really comes down to two simple steps. And I always like to start with the easiest and most obvious as it may save you time and a lot of hassle.

Step 1: Inspect The Edges For Overspill

In our experience, a hole in a liner is rarely the reason for water loss in a pond or water garden. Especially if you used a high-quality pond liner. Instead, it usually comes down to water spilling over the edge. This is especially common if you have a water feature like a waterfall, a stream, or areas where your liner may have settled down or landscape rocks have shifted.

First, fill your pond up to the desired water level, then visually inspect the edges of your pond for water spilling over. Tight turns in streams and to the left and right of a waterfall are two common places water may be spilling out. Also, check the outside perimeter of the pond for water pooling or damp areas. This is a tell-tale sign of water spillage.

If you’re not noticing any water spilling over and there are no damp areas around the pond or water garden, then let’s move on to step 2.

Step 2: Shut Down The Pump

If our check for the most obvious proved to be unfruitful, we now need to check the pond itself and its equipment. Shutting off the pond pump (and turning off your auto-fill valve if you have one) is the most crucial step in telling us where the water leak may be.

If your pond experiences water loss with the pump turned off, then the leak is most likely in the liner or foundation of the pond:

• The water will leak until it hits the spot where the tear or crack is. When the water leakage stops, inspect the lining or foundation around the surface of the pond water for the leak.
• If you’re struggling to find where the leak is, you can try using pond dye or the milk method to find the pond leak. Essentially, re-fill the pond with water just above the line of the tear and add a small amount of milk or pond dye to your pond water. This will cause the milk or dye, which you can easily see, to be drawn towards the hole. Using milk to find a leak in a pond liner is a very effective and low-cost pond leak detection system that is commonly used.

If your pond successfully held water while the pump was off, then the leak is most likely in the equipment or plumbing:

• Inspect any plumbing or external components you have like your skimmer box, external pond filter, waterfall box, etc.
• Water leaks are typically found in the fittings of your pipes and components so start there and tighten them if necessary.

Pond Leak Repair

If your water leak is in the foundation or liner of your pond, we’ll want to get it patched up immediately. And depending on your ponds foundation, there'll be completely different methods and pond sealers to use to repair your pond leak.

Choose your pond type from the guide below and follow the instructions to get your pond leak fixed as quickly and easily as possible.

Guide To Repairing Pond Leak’s

How To Repair A Pond Liner Leak

There are multiple ways to repair a hole in your pond liner and stop any water leakage. And the method you use will depend on the size of the hole. If the hole is less than 5” you can use an underwater pond sealant or a patch kit.

If using underwater sealant:

• Step 1: Simply clean the surface of the liner where the tear is.
• Step 2: Apply the sealer directly to the surface of the tear.
• Step 3: Allow curing for 24 hours.

*Note: you do not need to drain your pond to use underwater sealant. It can be applied and will cure under the water.

If using a patch kit:

• Step 1: Clean and wipe the area of the tear with a solvent wipe.
• Step 2: Scrub and dry the damaged area with a dry scrub sponge.
• Step 3: Remove the release paper from the patch and apply to tear.
• Step 4: Use a seam roller over the patch to ensure a tight bond.

If the tear is longer than 5”, you may want to consider replacing the liner.

How To Repair A Concrete Pond Leak

Once you’ve identified where the crack is in your concrete pond, you’ll want to seal it with a non-toxic sealer like Pond Armor’s Pond Sealer.

• Step 1: Prepare the surface (where the crack is) as per the directions of the specific sealer you are using.
• Step 2: Depending on the sealer you use, you may have to mix the sealer with a hardener.
• Step 3: Apply the sealer.
• Step 4: Let dry. Typically takes around 24 hours to fully cure.

Here's a video from Pond Armor on how to repair a cracked concrete pond using Pond Shield Epoxy.

How To Repair A Clay Pond Leak

For clay and soil foundations, which are typical for farm ponds, I recommend using bentonite for sealing ponds. Sodium bentonite is a natural clay that expands up to 15 times when exposed to water. This expansion fills in the cracks in the foundation of the pond and prevents it from leaking water.

• Step 1: Read the manufacturers directions. You may have to drain the pond below the damaged area. If you have a lot of cracks you may be better off draining the whole pond.
• Step 2: Apply the bentonite clay according to the manufacturer’s directions.
• Step 3: Refill pond back up to desired levels and monitor for leaks to make sure the crack was properly filled.

You can see how sodium bentonite clay works in this video from Natural Waterscapes.