Choosing your pond liner

The liner, otherwise known as the 'tarp', ensures the watertightness of the pond and is therefore essential. The choice of a pond liner is not easy when faced with the multitude of references available on the market. Let's try to see it more clearly...

Interests of the pond liner

• When creating a pond, the liner allows for unequalled freedom of shape.
• Generally less expensive than a preformed shell, the first prices remain accessible to most budgets.
• It also ensures a superior longevity and is not affected by frost and bad weather.

However, a geotextile felt should be slipped under the liner to avoid possible damage caused by roots or rodents.

Choosing a pond liner

The choice of liner depends on many criteria such as price, size and material.

Liners can be found in the form of rolls varying from 3 to 8 m in width and 25 to 60 m in length. If the dimensions of the liner are smaller than the size of the pond, it will be necessary to glue the strips together.

The 'first price' liners are generally made of PVC. There are three thicknesses: (0.5/0.8/1 mm). If you don't want to drain and repair your pond regularly, forget the first one! PVC liners are quite difficult to install because of the folds that inexorably form. PVC also poses some environmental concerns as it is difficult to recycle and toxic substances can migrate into the water. It is also a little sensitive to high temperatures, with a risk of softening for 'first price' references. However, a good quality PVC liner can last for 10 years.

Composite liners are appreciated for their extreme resistance and lightness. They are made of a thermo-bonded polypropylene sheet and 0.55mm polyolefin copolymers. Very innovative, these tarpaulins have an excellent flexibility and ensure an easy installation. They are resistant to cold and heat, as well as to traction and punching. These recyclable tarpaulins are more expensive (about 8 €/m²) than PVC liners, but they have practically nothing but advantages and are for the most part guaranteed for 25 years.

EPDM liners are recommended and used by professionals because they are very resistant, and come in long lengths and widths to create large ponds in any weather. They are available in thicknesses ranging from 1 to 1.14 mm.

A very good flexibility, a very high stretching capacity, a resistance to punching and to climatic hazards are added to these technical assets. This highly elastic synthetic rubber is easy to lay and does not wrinkle.

The lifespan of such a liner is at least 20 years. It is recyclable and compatible with aquatic life.

Creation of a pond in the garden

Introduce us to the project

We are working on the design of a pond. The clients wanted to create a nice atmosphere next to their terrace. We took advantage of the fact that the terrace is below the ground to create a pond within view when people are enjoying their terrace.

What type of pond was created here?

We are on a flexible form, which is why we chose an EPDM membrane. It is 300% elastic, which allows it to resist all the gravel and elements that could puncture the membrane. It is protected by a geotextile felt placed underneath.

How is the ground preparation done?

There are three points to consider:

• Never build this type of project too close to trees to avoid excess organic matter falling into the pond.
• Pay attention to the level during the earthwork. The water will quickly reveal the slightest defect as soon as it is filled.
• Protect the liner well to prevent it from wearing out over time.

How do you design a pond?

A pond can be decorated in a multitude of ways. Here, we decided on something quite elaborate with a small staircase and a small terrace area, where you can put a chair or watch the fish quietly. We wanted to play on the mineral and the vegetal by bringing blocks of schist and an olive tree. On this pond we have created a complete layout with a part that can receive a natural filter.

What is the principle?

The pond will be equipped with a pump that will feed two areas of the pond: a waterfall to create the atmosphere, enjoy the sound of water and for the aesthetic aspect and the second pipe will feed the natural filter at the other end of the pond.

The water will pass through a layer of gravel, in which irises are planted. The bacterial film that develops in this environment will filter the water, which is interesting in this type of pond with fish, because there is a lot of organic matter to filter.

We are going to use this process for the creation of natural pools, something that is already in place elsewhere even if we are not doing it yet. But we are looking into it.

So this pond is kind of a prototype in that respect. It's a large pond, but there are many ways to make a pond at home.

What materials can be used to create a pond?

Preformed resin ponds are the easiest to build because you just have to dig the hole.

You can also masonry the pond to obtain something very structured and rigid.

The third and most common solution is to install a liner.

Garden ponds

The option of a natural pond

For gardens with a natural atmosphere, the simplest solution is to create a lined pond to blend in with its surroundings. Once the construction is complete, the waterproof cover becomes invisible to the eye. And with the passing of the seasons, with the patina of time, the pond will give the impression of having always been there.

The option of a masonry pond

In a landscaped and structured garden, ponds with a waterproof coating have their place. More decorative than natural ponds, they are part of the architectural elements that structure the garden.

The reception of fish

A newly built pond cannot be used for fish. It is necessary that the nitrogen cycle is set up. The nitrogen cycle allows the degradation of organic waste into ammonia/ammonium, then into nitrites and finally into nitrates. This process takes about a month to set up. When the cycle is well balanced, the aquatic plants can be installed and the fish welcomed.

Aquatic plants

It is necessary to have one third of the volume of the pond occupied by aquatic plants so that phosphates and nitrates are properly absorbed.

Fortunately, aquatic species are numerous and easy to find at nurseries. A landscape gardener can provide good advice on how to harmonize them.

Maintenance of the pond water

To prevent leaves from falling into the pond and soiling the water, there are filtration systems that will eliminate all waste. It is true that the purchase of a pump and a filtration system has a cost, but if you do not wish to invest in this type of system, it will be necessary to regularly devote some of your time to cleaning and renewing the water.

Pond regulations

There is no particular legislation for the reception of fish and plants that are currently on the market.

As for the construction of this type of ponds, it is also outside the scope of the building permit and is therefore neither a declaration nor an authorization. For more information, it is best to contact your local city hall.

Creation of a two-level pond

What could be more pleasant than a corner of water in the garden near the terrace, which is more animated by the composition of two tanks at two different levels. Through an example of realization, let's discover how to realize the whole.

In this example, the pond is composed of two large rectangular tanks built into each other. The first, high tank is the largest volume of water. The second, lower level, is nested in a corner. At the back there is a planter and a technical room.

The upper pond

The upper pond is the largest volume, the height of the edge corresponds to the height of a bench to sit at the water's edge.

It receives the filtered water in the back left corner and has two overflows in the front right corner, consisting of two tubes that return the water to the lower pond. Thus, the level of the upper pond does not vary. On one of the overflows a vertical suction pipe for the bottom water is fixed. In case the overflow gets blocked, a gutter is placed in the corner to ensure an emergency overflow. 

A drain is provided at the bottom of the high pond towards the garden. This is closed by a plug.

The low pond

The lower square pond is placed in front of and partly embedded in a corner of the upper pond. It receives the water from the upper pond and acts as a buffer by absorbing the variations in water level due to evaporation. An overflow towards the garden is installed at the back right in case of excess water following winter rains for example.

At the bottom, a tube connects the pond to the technical room to connect the water circulation pump.

The technical room

The technical room of the installation is placed behind the low pond. An electrical area with a bar of waterproof plugs is provided as well as the arrival of the piping bringing the water from the lower pond. It receives the filter and the lighting of the pond.

The pump is calculated to circulate the total volume of water in a little less than an hour. In our example the volume is about 4m3 and the pump 5.5m3/h. The pump will be slowed down by the length of the pipes and especially by the filter.

The filter is sized accordingly. It is equipped with an ultraviolet lamp to prevent the development of green algae.

A waterproof lighting system is installed to illuminate the bottom of both ponds.

The plants

The deep pond will host a water lily and floating plants. Beware of the obstruction of the overflows by these plants.

The lower pond with its shallower depth will host tall plants such as marsh iris or horsetail, lower perennials such as water marigold whose pots will be enhanced by a cinder block and submerged plants such as milfoil. 

The plants are planted in pots with holes filled with a potting soil for aquatic plants with a thick layer of pozzolan on top to prevent the soil from going into the water and the fish from stirring up the soil by digging in. 

Getting started

Take advantage of the fall and winter months for the work and prefer early spring for the start-up of the pond. The sun is not yet too strong and the heat is not too great, so it is a good time to start and install the plants.