What's the Best Material for Pond Liners? Polyester or Rubber Pond EPDM?

The short answer

• Freeform, large volume or koi: EPDM liner on underlay fabric. It is the most versatile solution.
• Small pond and tight budget: PVC liner on underlay fabric, or preformed polyethylene shell.
• Small pond, quick to install, without cutting or folds: preformed shell, in polyethylene for the price, in polyester for rigidity.
• Contemporary garden, above-ground pond or straight walls: Corten steel pond.

Flexible or rigid: what really changes

A liner follows the hole you have dug. You design the shape, the shelves for plants and the depth, then the liner adapts to it. The freedom is total, but success depends on your excavation and soil preparation: stones and roots removed, protective fabric, neat edge.

A shell imposes its shape. You dig a hole to match it, you level it on a bed of sand and you fill it. The construction site is shorter and more predictable, but the volume, depth and shelves are those of the model. Impossible to enlarge them afterwards.

The four solutions in detail

The EPDM liner: the most versatile

EPDM is a very flexible synthetic rubber. Our Aquitechnics EPDM is 1.1 mm thick and remains flexible down to −45 °C: it is easy to handle, even in cool weather, and forms folds that are easier to distribute in the corners. It is available in 11 roll widths, from 3.05 m to 15.25 m, and can reach up to 930 m² in one piece, without a joint. It is the solution we recommend for freeform ponds, large volumes and koi ponds.

It is always placed on a 400 g/m² protective fabric, which protects it from stones and roots. In case of an accident, it can be repaired with EPDM-specific glues and accessories.

The PVC liner: the most economical

PVC costs less to buy and weighs less than EPDM. It can be glued or welded, and small damage is easily repaired. In return, it stiffens over time and under UV rays, and it is less flexible in cold weather. It is well suited to a small ornamental pond when the budget matters. It is also placed on fabric.

The preformed shell: the fastest to install

The polyethylene (PE) shells are lightweight and economical, from a hundred liters to about 1,500 liters. They are ideal for beginners. The polyester shells are more rigid and more durable; they are available in rectangular, round or natural shapes, and several models can be placed underground or above ground. In terms of repair, polyester is easy to repair, polyethylene much more difficult.

Their limit: depth. Most shells do not reach the 80 cm to 1 m we recommend so that goldfish can overwinter outdoors. If you want fish, choose the deepest shell possible.

The Corten steel pond: the most architectural

For a contemporary garden, Corten gives clean walls and a rust color that patinas. The inside of our ponds is coated with a 2 mm polyurea. They are delivered with two 1-inch threaded fittings and an overflow; several models optionally accept a wall with a water blade and LED lighting. Custom dimensions are possible.

The comparison table

On mobile, swipe the table to the left. Relative budget: comparison between solutions with equivalent water surface, installation included.

The decision tree

Three questions are enough in the vast majority of cases. Start at the top, and follow "yes" to the right.

Still hesitating between two branches? Our general comparison on garden pond waterproofing expands the question to concrete and on-site laminated polyester.

The steps to choose correctly

1. Define the use. Plants only, goldfish or koi: this is what determines the minimum volume and depth.
2. Set the depth. For goldfish that overwinter outdoors, plan for a zone of 80 cm to 1 m. Check if a shell reaches it; otherwise, switch to a liner.
3. Draw the shape. Trace it on the ground with a garden hose. A freeform or shelves to your liking point towards the liner; a clean rectangle, towards Corten or a shell.
4. Choose the material. Follow the decision tree above, then compare the models in our collections.
5. Calculate the dimensions. For a liner: length or width of the pond + 2 × maximum depth + edge on each side. Our guide for calculating and ordering the right size of EPDM liner details the method.
6. Plan the equipment. Filtration, pump and aeration depend on the volume. Our custom equipment selector calculates them from your dimensions.

Our solutions

The pre-ordering checklist

• I have defined the inhabitants: plants, goldfish or koi.
• The planned depth is suitable for these inhabitants (80 cm to 1 m for goldfish that overwinter outdoors).
• For koi, the volume reaches about 5 m³ at a minimum.
• I have traced the shape on the ground and checked access for digging.
• For a liner: I have calculated the two dimensions with the maximum depth and the edge.
• For a liner: the protective fabric is planned over the same surface.
• For a shell: I have noted its overall dimensions and its actual depth.
• I have planned an electrical supply for the pump and filter.

Frequently asked questions

What lasts longer, a liner or a polyester pond?

A well-placed EPDM liner on fabric and a polyester shell are both durable solutions. The PVC liner stiffens faster with UV rays, and the polyethylene shell is the least easy to repair.

Can you put koi in a preformed pond?

Generally, no. We recommend about 5 m³ at a minimum for koi, with serious filtration. Most shells are much smaller: a koi pond is almost always built with an EPDM liner.

Can goldfish overwinter in a shell?

Yes, if the shell is deep enough. We recommend a deep zone of 80 cm to 1 m for overwintering outdoors. Many shells are shallower: check the actual depth of the model before buying.

Is fabric needed under an EPDM liner?

Yes, always. The 400 g/m² fabric protects the liner from stones, roots and friction. It is placed over the entire surface covered by the liner.

Can you repair a punctured liner or shell?

An EPDM liner is repaired with specific glues and accessories, a PVC liner by gluing or welding. A polyester shell is easy to repair; a polyethylene shell much more difficult.

What is the maximum size of an EPDM liner?

Our Aquitechnics EPDM exists in 11 widths, up to 15.25 m, and can reach up to 930 m² in one piece, without a joint. Beyond what the pack offers, we make custom liners.