Water loss from a backyard pond is a common concern. The dilemma is determining whether the water is being lost to a leak or simply to natural evaporation. Evaporation is a continuous, natural process, while a leak represents a structural failure requiring repair. Distinguishing between these two causes is the first step in maintaining a healthy water feature, and it can be determined through simple, controlled testing and observation.
Understanding Normal Water Loss
Water naturally transitions from a liquid state into vapor, known as evaporation, which is the most frequent cause of a dropping water level. The rate of loss is governed by several environmental factors, making the “normal” loss rate variable across different days and seasons. Air temperature plays a significant role, as warmer water molecules possess more energy and are more likely to escape the surface tension and become airborne vapor.
Wind substantially increases water loss by carrying away moist air above the surface, allowing drier air to replace it and absorb more moisture. Low humidity levels further accelerate the process because the surrounding air has a higher capacity to hold additional water vapor. In hot, dry, or windy conditions, a pond can lose between one-quarter and one-half inch of water per day. Water features, such as waterfalls and streams, also contribute to this normal loss because they increase the water’s surface area exposure, encouraging greater evaporation.
The Controlled Diagnostic Method
The most definitive technique for separating evaporation from leakage is the “Bucket Test.” This controlled experiment isolates the effect of evaporation on a small, contained body of water and compares that loss to the water loss in the pond itself. To begin, fill a five-gallon bucket with pond water and place it on a submerged shelf or step so it is partially immersed near the edge of the pond. The water level inside the bucket must match the water level of the pond outside the bucket.
Make a permanent mark on the inside wall of the bucket to indicate the starting water level, and a corresponding mark on the pond liner to show the pond’s starting level. Before starting, turn off any automatic water-fill devices and pumps powering waterfalls or streams. Monitor the test over a period of 24 to 48 hours to obtain an accurate reading.
After the monitoring period, compare the drop in water level inside the bucket directly to the drop in the pond’s water level. The bucket’s water loss represents only evaporation and precipitation. If the pond level has dropped a greater distance than the bucket level, a leak is confirmed in the pond structure. Conversely, if both levels have dropped by the same amount, the water loss is due only to natural evaporation.
Identifying Physical Leak Indicators
If the bucket test indicates a leak, the next step is a focused physical inspection to pinpoint the source of the water loss. A common location for leaks is around the perimeter, often due to a low edge or settling liner allowing water to spill over. A careful walk around the pond’s border can reveal saturated soil, unusually lush patches of grass, or muddy areas, all signs that water is escaping the containment area.
If the pond has water features, such as a waterfall or stream, the leak may be occurring there instead of the main basin. A useful diagnostic technique is to let the water level drop without refilling it while the pump remains off. If the water loss stops once the level falls below a specific point, such as the skimmer opening or the top of the waterfall, the leak is located at or just above that stabilization point. If the water level continues to drop past the lowest feature, the leak is likely a tear or puncture in the primary liner material within the pond basin.