4 Reasons Your Pond Is Losing Water

Reasons Your Pond Is Losing Water

It’s normal for a garden pond to lose water on hot days and during heatwaves. Evaporation is one reason, but if your pond is regularly losing water even when the sun isn’t strong, there could be other causes. Learn more about the reasons for water loss and how to address them.

How Much Water Can Your Pond Lose?

On hot summer days, it’s entirely normal for your garden pond to lose water due to evaporation. The increased water requirements of plants in the shallow-water and shoreline zones during heatwaves can also contribute to higher water loss. There’s no one-size-fits-all answer to what constitutes normal water loss, as it depends on factors such as your pond’s size, plant population, location, and sun exposure. During summer heatwaves, your pond’s water level may drop several centimeters daily, which is normal. When topping up your pond with tap water, do it slowly to avoid shocking your fish with cold water. Matching the water temperature to your pond water can help prevent temperature shock. You can achieve this by using a container to let the water warm up before adding it to your pond.

Significant Water Loss and Its Causes

If your garden pond consistently loses significant amounts of water, it’s essential to identify the cause. Not all water loss issues are related to holes in the pond liner.

Holes in the Pond Liner

The most common cause of water loss in your garden pond is holes in the pond liner. These defects can occur with low-quality, thin liners or, over time, even with high-quality liners as they lose their flexibility and become brittle. Depending on the quality of the liner, you can expect it to last between 15 to 25 years. When the liner ages, it may develop tiny holes. Even a high-quality liner can develop holes from folds, creases, foreign objects like sharp stones or glass, and the roots and rhizomes of plants. If part of the liner is exposed to intense sunlight, UV light can cause damage.

Detecting Holes in the Liner

If your pond loses water without strong sunlight, start by examining the liner for possible damage. It may not be necessary to drain the water completely. Begin by filling the pond with water and marking the water level daily with chalk on the liner. If the water loss becomes less pronounced, you will have narrowed down the area where the defect likely exists. Thoroughly clean and inspect the identified section of the liner for damage, including looking for holes. Larger holes are usually easy to spot by touch. Check for damage in folds and creases as well. If the water level keeps dropping, a damage spot may exist at a lower point, which requires more extensive investigation. Temporarily relocate fish and aquatic plants using an inflatable pool or a plastic container. Drain the water and use a pond vacuum to remove the silt, allowing you to inspect the liner’s bottom. If you still can’t locate the leak, fill the pond with fresh water and sprinkle flour on the surface. The water flow will carry the flour to the point of the leak.

Repairing the Liner

Once you’ve found the hole, you can proceed with the repair. Patching the defect involves attaching a new piece of liner. You may need to remove some water from the pond, depending on the patch size. The patch should overlap the damaged area by at least 15 to 20 centimeters on all sides. If there’s a foreign object beneath the liner causing the leak, enlarge the hole to remove it. Fill the area with expanding foam or a synthetic fabric. Thoroughly clean the section of the liner that needs to be fixed before sealing the hole. Use a special adhesive and waterproof glue for PVC liner repair or adhesive and double-sided tape for EPDM liner repair.

Water Loss Due to Capillary Action

Water loss in your garden pond isn’t always due to liner damage. Another possible cause is capillary action when the liner edge is buried below the soil surface. In this case, the surrounding soil draws water out of the pond. If you notice marshy soil near your pond, this may be a sign of capillary action. To prevent this, you can create a capillary barrier between the pond and its surroundings. You can add a capillary barrier post-construction using plastic profile systems. These profiles are available by the meter and should be fixed to suitable stakes. Ensure the gap between the stakes is not too wide to prevent the profiles from being pushed outward by water pressure. When the liner is large enough, you can also construct a capillary barrier by digging it up, pulling the liner over a small earth wall, and then burying it again.

Choosing the Wrong Plants

Water loss can occur due to the presence of the wrong plants in the shallow-water and shoreline areas. Plants like reeds and bamboo have strong, penetrating runners that can damage your pond liner. To prevent this, use a polyethylene rhizome barrier that’s around 80 centimeters tall. Consider alternatives to bamboo and reeds that don’t spread as aggressively. If your shoreline vegetation is dense, water loss can also result from the transpiration of marsh plants. Trim your plants and thin out the vegetation to help conserve water.


It’s typical for a garden pond to lose water on hot summer days, but if your pond is losing a significant amount of water regularly, there may be an underlying issue. Often, the problem is a damaged pond liner, and you can identify and repair the defect. Other potential causes of water loss include a lack of capillary barrier, issues with the filter system, or incorrect shoreline and shallow-water plants.

Water Loss Due to Hose and Filter System Defects

Defects in the hoses or filter system can also lead to water loss in your garden pond. To determine if this is the cause, turn off the pump and fill the pond with water. If the water level remains consistent over the next few days, this could indicate a filter system leak. Inspect the filter system closely and replace any damaged components.

Florian Egert

I am Florian Egert, the owner of pondlovers.com. I live with my wife and two children in Germany in a small village in the countryside.

Recent Posts