Leaking Ponds: Causes and Troubleshooting

Molly Jones, Regional Water Resources Agent

Ponds are not typically a natural occurrence in the state of South Carolina. Our state’s specific geological and hydrological characteristics are not conducive to the natural occurrence of lakes or ponds due to a few factors: flat topography; the majority of South Carolina is a coastal plain, which does not allow for natural depressions, rapid drainage; sandy soils allow water to percolate quickly into sediment layers down into the groundwater system, and geological age; South Carolina was not affected by geological activity during the last ice age so it was not carved by these ice formations. Most of the lakes and ponds in our beautiful state are man-made. Natural cycles create a need for tailored management of all man-made ponds and lakes.    

Water loss in ponds can be alarming for pond owners and managers. Water loss can be attributed to multiple factors, such as leaking or evaporation. Identifying if a pond is losing water due to evaporation or leakage can prevent pond managers from spending a significant amount of time and money troubleshooting. Normal evaporation can cause water levels to drop by 0.25 to 0.5 inches per day during hot, dry summer months. If the pond shows a loss of 2 inches or more per month, it is likely to lose water due to leakage. How can you, the pond manager, determine evaporation vs leakage? The bucket method is a good start!

The Bucket Test

1. First, fill a bucket 1-2 inches from the top.
2. Place the bucket on a flat shelf or step inside the pond. The bucket needs to be submerged 5-6 inches so that the water inside the bucket stays the same temperature as the water in the pond. You may place a heavy object in the bucket, such as a brick, to keep it stable (make sure to mark the water level after you’ve placed the brick in the bucket).
3. You will mark the water level inside the bucket (bucket’s water level) using a permanent marker.
4. On the outside of the bucket, mark the pond’s water level using a permanent marker.
5. Wait 24-48 hours, leaving the pond undisturbed (do not add any water to the pond during this time).
6. Check the water levels in the bucket and outside (the pond). If the levels have dropped close to the same amount, this is evidence of evaporation. If the pond has dropped faster than the bucket, there is a high likelihood of leakage. 

My pond is leaking… What can I do?

First, it is important to identify what is potentially causing the leak. The most common causes of leaks are construction issues, biological damage, and geological factors. Construction issues can include inadequate compaction/thickness of the clay layer in the pond and dam failure, or leaks around outlet pipes that rust. Some typical biological factors include roots from trees planted on the dam, which can create weak points and allow water to leak out, water-loving trees such as willows and maples often grow around banks of the ponds, these trees can contribute to water usage of up to 12 inches each month, and burrows from wildlife such as beavers and muskrats. Geological factors may include the presence of sand, gravel, or porous bedrock like limestone at the pond basin. There may be biological signs of leakage in areas around the pond. The presence of water-loving plants at the base of the pond dam or base may point to the source of the leak.  A thorough inspection of the pond by a pond management company and/or an engineer specializing in dams is highly recommended.

Managing a leak can be minimal or extensive, depending on the severity of the leak. In minimal leak situations, adding water to the pond to make up for water loss is the best option. Often, ponds are filled by a nearby stream or spring, and sometimes by a groundwater well. If utilizing a groundwater well, especially if the well supplies your home, it is important to do so with caution to not dry up the well source, especially during drought conditions. A more extensive approach to fixing a leaking bottom experiencing seepage due to poor soil compaction is to drain the pond completely and re-compact the bottom utilizing a roller to help reseal the soil. Clay liners may be utilized to repair leaking areas and must be 12 inches thick after compacting. Bentonite is a popular product utilized for sealing a pond bottom. It is most effective when applied to a dry pond bottom and tilled into the soil. Bentonite is a clay substance that expands when wet.  Chemical additives are another option that can be added to the soil to improve a watertight seal. This method works best on soils with 15% or more of clay. The most common chemical additive used is sodium polyphosphate. Plastic liners can be an option for smaller-scale ponds with recurrent leaks.  

For additional information on these methods, please read Fixing a Leaking Pond by Bryan Swistok, Pennsylvania State University.

For a list of resources and pond management companies in South Carolina, visit  https://www.dnr.sc.gov/fishpond/index.html

References

Primary Extension Guides

• Penn State Extension: “Fixing a Leaking Pond.”
  • Key Content: Provides detailed methodology for the “bucket test,” chemical additives like sodium polyphosphate, and the application of bentonite and plastic liners.
• Clemson Cooperative Extension: “Stormwater Ponds: Inspection and Maintenance Considerations.”
  • Key Content: Offers specific guidance for South Carolina pond owners, focusing on shoreline erosion, dam safety, and structural maintenance.
• Ohio State University / Ohio DNR: “Ohio Pond Management Handbook.”
  • Key Content: Emphasizes soil requirements (minimum 20% clay) and geological considerations for preventing and fixing seepage.
• K-State Research and Extension: “Leaking Farm Ponds.”
  • Key Content: Technical instructions for using sheepsfoot rollers and clay blankets (1–2 feet thick) to seal leaking farm pond basins. 

Federal Technical Standards

• USDA Natural Resources Conservation Service (NRCS): “Ponds—Planning, Design, Construction” (Agriculture Handbook 590)
  • Key Content: The foundational national standard for pond construction and repair, often cited by all state extension offices for engineering specifications. 

Additional Regional Resources

• Texas A&M AgriLife Extension: Pond Management Resources
  • Key Content: Extensive library on managing recreational and farm ponds, including leak repair in arid climates.
• Mississippi State University Extension: Pond and Lake Management
  • Key Content: Focuses on the “Golden Rules” of pond construction to prevent leaks. 

Clemson University Cooperative Extension Service offers its programs to people of all ages, regardless of race, color, religion, national origin, disability, political beliefs, orientation, marital or family status and is an equal opportunity employer.