How to Find and Fix a Pond Leak

Reader Contribution by Darrell Rhoades
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Is it a pond leak or evaporation? One thing to help determine if it is leaking is if we are in spring weather with snow melt and rain and the pond is still going down. What we are looking for is if we have water coming in to supply the pond, is the pond continuing to lose water?

If this is the case, then we most likely have a leak somewhere. The leak could be anywhere in or around the pond. But if we are in the summer months with no rain or water entering the pond, evaporation could be lowering the pond level. Hot dry days can suck up to 1 inch of water a day so pay attention to the weather as well before we assume there is a leak.

There are plenty of areas in the pond where a leak could develop over time or the pond may have never have filled up in the first place.

Let’s get started and poke around in areas that could be leaking this is to help get you thinking of the possibilities where to look and if you’re building a pond to be sure to pay attention to some of these areas listed below.

Finding the Pond Leak

On a new pond build was the entire site compacted? If so, is the entire area of good clay content? Remember that the entire site needs to be compacted; digging a hole in the ground typically will not work. The exposed new earth is now like a sponge allowing water to penetrate and keep weakening the pond basin area. The other problem is if there are multiple layers of earth, like top soil, clay, gravel and sand, finding a vein or porous material will allow the pond to leak.

Start on the outside of the dam look for greener areas in the grass, depressions, cracks, rooted vegetation such as trees and any moist or damp spots. Finding any of these could mean a structural problem with the dam.

Another common problem area is with new or an old pond is the outlet pipe. Take a look at the pipe, water should only come out of the inside of the pipe. If any water is coming around the outside this is a dangerous situation and needs corrected. Getting more pure clay from the local gravel pit or your property is cheaper in costs than ordering in products since they are heavy and add to shipping costs. Take the clay and pack around the pipe on the water side of the dam, nice and thick like a foot or more to seal around the pipe and get the water to stop leaking. If it continues to leak it will only get bigger which could cause the dam to fail. Older ponds may have the metal pipe which could be rusting out and would need to be replaced.

Does the pond stop leaking down? Is there a level at which it seems to slow or hold? If so then somewhere around the new water level is most likely your leaking area. Take a pole or shovel to investigate for gravel or sand areas—even soft spots where the water level has stopped along the new shore line. If you find a poor quality area it should be dug out and re-filled with clay.

What if the pond empties completely? Now we are looking at the floor of the pond for gravel, sand or soft areas that could be letting the water seep out. Even a pond built down to bedrock or slate for the bottom will leak out the top of the rock. Or look at the smooth plastic pipe going through the dam? Water will seek out the path of least resistance and follow the smooth surface, leaking out and potentially getting larger over time. One way to fix the slate bottom is to build the pond higher than the slate leaving a foot or two of clay on top of the slate. Or get through the rock plate and seal the exposed rock.

Fixing the Pond Leak

Above I talked a lot about using local clay from your property or a gravel pit near you, the reason is clay is very heavy and shipping it in from a great distance will run the costs up just for shipping it to your pond.

There are other products on the market to repair leaking ponds and two of the companies I have spoken to, and we have an interview with one to learn more about their product. The other product works as well but more in line of slower leaks so first up is Pond Seal.

Pond Seal, a tiny stone that is surrounded by compacted sodium bentonite forming a small stone shape a little smaller than pea gravel. The whole concept is that the pond seal can penetrate the water and go to the leaking area, provided you know where the leak is such as a 4-by-4 pounded into the pond floor or if you know where there may be a gravel area during the building process. The pond seal can also be used as a liner in a new pond or a full pond providing the application covers evenly at 7lbs per square foot rate. Pond Seal is relatively inexpensive, but depending on the amount needed the cost can grow, and don’t forget about shipping cost too. On average shipping three 50 lbs bags will cost the same as the material itself.

Next up is ESS-13 which can be applied on the water, sprayed or treated and compacted in to the soil. This product is for soils that are able to be compacted but not hold water. There are some requirements to use the product such as a way to mix the product in the pond water like a fountain or proper sized aeration system and to have incoming water to keep the pond full while the product gets distributed throughout the pond. What happens is the material will seep into the leaking area, start to collect and expand to fill in the tiny pores that is allowing water to leak out. So you see if the leak is too rapid or the pores are too large the material will just be washed out. There is a slight caution on using this product if you have fish; this is taken right from their website for the waterborne application.

“The phenomenon of the occasional ‘fish kill’ is one that people involved in pond management are familiar with. There are many contributing factors that can trigger this event and often several of them need to occur simultaneously. Some of the most common are: low dissolved oxygen, high water temperatures, prolonged cloudy weather, excessive algae, and overcrowded populations.

Over the last 50 years of sealing lakes, ponds and lagoons, Seepage Control, Inc. has occasionally seen a fish kill after a waterborne treatment of ESS-13. Other times the aquatic environment has seemed to thrive. There has been speculation that the oily nature of the product causes a mechanical disruption to respiration in fish, however this idea has not been confirmed. Seepage Control, Inc. contacted the Marinco Bioassay Laboratory located in Sarasota, Florida to run tests to determine the toxicity of ESS-13 on the aquatic environment.

The lab ran standard toxicity tests on Fathead minnows (Pimephales promelas) and Daphnia (Daphnia magna) to determine LC50 values for the product (lethal concentration that causes 50% mortality in a test sample). The testing shows that the product is non-toxic and any effect on the organisms is at concentrations significantly higher than our standard treatment. While the occasional loss of fish is unfortunate, we are pleased to see the lack of toxicity of ESS-13 shown by these tests.”

If you are spraying or treating and compacting there would be no worries of harming the fish. You can Contact Seepage Control for more information.

This whole process of finding the leak can be very time consuming, but remember how the pond has acted over the years, the rain fall amount, what time of year the pond drops, whether it always go to the same level, and if there are trees around the pond. These are a few things to think about and they can help you get a better idea of where to look. Once there is a potential area of concern, then it is time to act.

One last note on the leaking pond, many folks are excited about having water coming in while they dig their pond, although it’s a pain for the equipment it seems to be a good sign the pond will fill up. Remember where these springs or seeps are for future reference. Over time things can change such as the water table level. Even the water that has come into the pond over the years can be a potential leak if the spring should dry up, basically draining the pond.

There are other thoughts on the causes of pond leaks, such as the new well drilling and the fracking of gas wells, even a tremor or small earth quake can be a culprit.

With this said, we also want to watch the hot dry summers. As the water recedes and the ground becomes hard and cracked, these cracks can also be an area of a future leak. As the water level rises, the clay hasn’t had time to soften and seal the crack; water can pass through to the porous ground and leak out.

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