What is a capillary barrier in a pond?

What is a capillary barrier in a pond

When creating a garden pond, don’t forget the capillary barrier. Without it, water losses due to the capillary effect are common. Like a wick, the surrounding soil draws water from the pond. The capillary barrier separates the pond from its surroundings and its vegetation. You should consider the capillary barrier during the planning of your pond. If your pond already exists, and you forgot the capillary barrier, it can still be installed later.

A capillary barrier – what is it?

The capillary barrier, also known as a suction barrier, separates the garden pond from its surroundings. It prevents the pond from losing water due to the capillary effect. This capillary effect occurs when the area around the pond and the plants growing there extract water from the pond. If there is no capillary barrier in your garden pond, you can identify water loss due to the capillary effect when the soil in the vicinity of the pond becomes very marshy. Like a wick, it draws water from your garden pond. On hot summer days, the pond can lose significant amounts of water due to the capillary effect. The capillary barrier also prevents plants at the edge of your garden pond from growing into the pond and, conversely, prevents plants from the pond from spreading into its surroundings. It serves as a pond shoreline reinforcement. The capillary barrier marks the transition from the pond liner to the shore.

Capillary barrier as a clear separation between the pond edge and planting

The capillary barrier separates the pond edge from its vegetation and encircles the entire pond. It prevents the infiltration of nutrients into the pond, for example, after heavy rain. Thus, the capillary barrier helps to keep the water in your pond cleaner and reduces the formation of algae. It prevents the impairment of water oxygenation by the entry of nutrients into the pond. The capillary barrier contributes to better water quality. If your pond loses a lot of water on hot summer days due to water being extracted by the roots of nearby ground vegetation, the water level can drop significantly. This promotes the development of microorganisms and worsens water quality. Moreover, you’ll need to constantly refill the pond, incurring high costs. If there are fish in your pond, the constant refilling with cold water can be very stressful for them on hot summer days.

Consider the capillary barrier in the pond’s planning

If you are planning to create a garden pond, you should think about the capillary barrier during the planning phase. When buying and laying the pond liner, consider the capillary barrier, as the liner should extend 60 to 80 centimeters beyond the actual pond edge. After you have placed and welded or glued the pond liner into your garden pond, fill it with water. Only then should you finish building the pond edge since the liner will be drawn a few centimeters into the pond pit by the water. Only the root protection fleece and the liner should extend into the surrounding terrain to prevent the capillary effect.

If you opt for a ready-made pond with a raised edge, you don’t need to create a capillary barrier. The edge of the ready-made pond already serves as a capillary barrier. For the capillary barrier of a pond liner, it must be significantly above the water level of the pond. Contact and exchange between the pond and its surroundings must be permanently interrupted.

It may not look very attractive when the liner extends beyond the garden pond’s shore. However, this is necessary for the capillary barrier of a liner pond. You can cleverly hide the liner’s edge with a gravel layer and create an aesthetically pleasing shoreline design.

How to install a capillary barrier – step-by-step guide

If you are creating a garden pond, follow these steps to create the capillary barrier:

  • Excavate the pond and prepare it completely.
  • Dig a trench around the entire pond pit, about 20 centimeters wide and 20 centimeters deep.
  • Line the pond with a liner, and extend the liner 60 to 80 centimeters beyond the entire pond edge. It should reach into the excavated trench.
  • Fill the deep-water zone of your pond with water, allowing the liner to adapt to its surroundings.
  • Fill the trench around your pond with gravel.
  • Fill the pond’s edge with gravel or soil to create an attractive appearance.

Different options for the capillary barrier

To create a capillary barrier, you have several options. The easiest is a suction barrier with a gravel layer, for which you need to excavate a trench, as described earlier. This capillary barrier requires corresponding maintenance since over time, plants around the pond can grow into the gravel layer. To prevent this, consider installing a plastic root barrier for the plants on the pond’s edge.

An alternative is a capillary barrier along the pond’s edge. You can create a pathway around your pond, and fill the trench around the pond with concrete. This creates a stable foundation for the pathway’s slabs. However, if you ever want to remove the concrete, damaging the pond liner is inevitable.

If you have a terrace, you can create your pond near it. The terrace serves as part of the capillary barrier. Along the terrace, you construct a base from concrete almost immediately by the pond. Extend the pond liner over this base. Then, place terrace slabs on it.

Adding a capillary barrier later

If your garden pond already exists and lacks a capillary barrier, you can still install it later. You can obtain various pond edge systems for this purpose, which can also compensate for uneven terrain and varying shoreline heights. These systems are offered as rolled goods with different lengths and heights. They are usually made of plastic and are flexible. To install such a pond edge system, you’ll need stakes to drive into the ground. The distance between the stakes should not be greater than 50 to 60 centimeters, as the water pressure could otherwise deform the pond surroundings. Attach the pond edge system to these stakes. Such a pond edge system can also serve as a rhizome barrier for shoreline plants.


A capillary barrier prevents water losses in your garden pond by separating the pond from its surroundings. It ensures that the surrounding soil and plants on the pond’s edge do not extract water from your garden pond. The roots of the surrounding plants cannot grow into the pond. Conversely, plants in your pond cannot grow into the surrounding area. You should consider the capillary barrier during the planning of your pond and include it when calculating the pond liner. If there is no capillary barrier, it can be installed later with a pond edge system.

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.

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