Water loss from a pond is common, but excessive or rapid drops suggest a structural issue. Successfully keeping water in a pond requires a systematic approach: first identifying the nature of the loss, then minimizing natural depletion, and finally employing the correct repair methods for structural leaks. Understanding the difference between expected evaporation and an actual breach is the first step in maintaining a healthy pond ecosystem.
Diagnosing the Cause of Water Loss
The first step is determining if the loss is due to a physical leak or high rates of evaporation and splash. This distinction is made using the “Bucket Test.” To perform this, fill a container with pond water and place it on a submerged ledge so its water level matches the pond’s. Mark both the container’s interior and the pond’s exterior water level, then leave the system undisturbed for 24 hours.
If the water levels drop by the same amount, the loss is due to evaporation, as both bodies were exposed to the same conditions. If the pond’s exterior level drops more than the container’s, a structural leak is present, requiring the “drop-down method.”
Turn off the circulation system, including waterfalls and streams, to isolate the main pond body. If the water level stabilizes, the leak is in the circulation system or plumbing. If the water continues to drop, it is a static leak in the pond basin. The water will fall until it reaches the exact height of the breach, pinpointing the leak’s location along the perimeter.
Leaks often occur where the liner or shell meets the landscape, or around mechanical parts like the skimmer faceplate or filter connections. Once the water level stops dropping, thoroughly inspect the liner or shell material at that specific height to find the exact point of escape.
Strategies to Minimize Natural Water Loss
Some water loss is unavoidable due to evaporation, which is accelerated by high temperatures, direct sunlight, and wind. Reducing the water temperature and limiting surface exposure significantly lowers this natural rate of depletion.
Adding shade over the pond’s surface minimizes evaporation by blocking solar radiation. Shade can be provided by planting nearby trees or shrubs, installing trellises, or using aquatic plants like water lilies that cover a portion of the surface. These plants also help cool the water by absorbing solar energy.
Splash loss occurs when water features cause droplets to land outside the pond basin. Careful adjustment of waterfalls, streams, and fountains is necessary to ensure all water is directed back into the pond and not splashing onto surrounding rocks or land. Adjustments to the flow rate or rock positioning can redirect the water’s trajectory back into the containment area.
Capillary action, or “wicking,” happens when porous materials at the pond’s edge draw water out of the basin. This occurs when soil, gravel, or underlayment fabric contacts both the pond water and the surrounding dry ground. Installing a capillary barrier, typically by folding the liner up and over the edge and backfilling with non-porous material, prevents this slow draining effect.
Structural Repairs for Pond Leaks
Once a structural leak is identified, the repair method depends entirely on the pond’s construction material.
Liner Ponds
For ponds built with flexible EPDM or PVC liners, use a specialized repair kit containing a patch and compatible adhesive or primer. The area around the tear must be thoroughly cleaned and dried, often with a solvent like acetone, before applying the primer and firmly pressing the patch onto the damaged section.
Rigid and Concrete Ponds
Pre-formed ponds (plastic or fiberglass) and cracks in concrete can be fixed using a two-part epoxy or a flexible sealant designed for underwater application. Concrete structures with larger cracks may require hydraulic cement, which sets rapidly and cures even when submerged. Hairline cracks require a specialized concrete sealant pressed into the fissure to create a watertight barrier.
Earthen Ponds
For earthen or natural bottom ponds that lose water through seepage, the solution involves creating a new, impermeable layer. Sodium bentonite clay is the most common material, as it expands significantly when hydrated, filling voids in the soil. The clay is applied using a blanket method (spread over the bottom and covered with soil) or mixed directly into the existing soil and compacted.
Liquid Sealants
Liquid rubber or specialized polymer sealants can treat porous bottoms or be used for larger repairs on liner ponds, creating a seamless, self-adhering membrane. This liquid application covers a larger area and is useful where multiple small leaks are suspected but not precisely located. Proper application requires following manufacturer instructions regarding surface preparation and curing time to ensure the repair is permanent and safe for aquatic life.