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The liner is the one part of a garden pond you hope never to think about again. Once it is buried under water, plants and edging stones, replacing it means draining the pond and starting over. That is why it pays to choose carefully, whether you are digging your first wildlife pond or relining an old one that has started to leak.
Late autumn and winter are good times to plan, because ponds are quiet and you can be ready to dig as soon as the ground allows. In this guide we compare the five types of liner sold by Pondkeeper, the UK pond specialist, show what a 3m x 3m liner costs in each and explain how to size and protect it. Prices are from pondkeeper.co.uk at the time of writing.
Shop Pond Liners at Pondkeeper
In this guide
What a Pond Liner Does
A pond liner is simply a waterproof sheet that keeps water in the hole you have dug. Without it, the water would soak into the ground. Pondkeeper explains that most liners are made by joining sheets of fabric together in the factory, and these seams are very strong. The main differences between liners are the material, the thickness, how flexible they are and how long they are guaranteed for.
Five Liner Types Compared
| Liner | Material and thickness | Key strengths | Price for 3m x 3m |
|---|---|---|---|
| Flexiliner | LDPE, laminated with a UV-resistant coating | Cheapest, light, tearproof, 15 to 40 year guarantees | £17.91 (15 year) to £26.91 (40 year) |
| PVC | 0.3mm or 0.5mm PVC | Slight stretch, good for simple shapes | £29.61 (15 year) or £34.11 (30 year) |
| EPDM rubber | 0.75mm synthetic rubber | Very flexible, tear-resistant, weatherproof | £85.41 |
| Butyl rubber | 0.75mm synthetic rubber | Excellent puncture resistance and UV stability | £103.41 |
| Firestone EPDM | About 1mm heavy-duty rubber | Thickest and toughest, longest lasting | £119.54 (3.05m x 3.05m) |
Flexiliner: Best Value
Flexiliner is Pondkeeper’s own exclusive liner and its best seller on price. It is made from LDPE, or low density polyethylene, woven very tightly and then laminated on both sides with a UV-resistant coating for long-term outdoor use. Pondkeeper says it is tearproof, meaning a small puncture made during installation will not run into a bigger tear. It is also light and flexible enough to bed into corners, and comes in more than 90 sizes.
You choose the guarantee you want. A 3m x 3m Flexiliner costs £17.91 with a 15 year guarantee, £22.41 with 25 years or £26.91 with 40 years. See Flexiliner sizes and prices.
PVC: A Step Up
PVC is the next step up in price. Pondkeeper sells two weights, 0.3mm and 0.5mm, which it has found to be the best for this fabric. PVC has a slight stretch that LDPE does not, but Pondkeeper notes that it is heavier and not tearproof. It is a good, affordable choice for simpler, rectangular ponds. A 3m x 3m PVC liner costs £29.61 with a 15 year guarantee or £34.11 with 30 years.
Rubber Liners: EPDM, Butyl and Firestone
EPDM and butyl are both synthetic rubber liners and are the choice of many professional pond builders. Pondkeeper explains that butyl has a higher natural rubber content but has become very expensive, because the same polymer is in demand for products such as car tyres. Most of the pond market has moved to EPDM, which looks and feels almost the same, costs less and, according to Pondkeeper, actually offers better characteristics.
Both are 0.75mm thick at Pondkeeper, and a 3m x 3m sheet costs £85.41 in EPDM or £103.41 in butyl. For the strongest option, Firestone EPDM is about 1mm thick and built to last, though Pondkeeper warns that it is harder to move into position around curves. A 3.05m x 3.05m Firestone liner costs £119.54. Most rubber sizes are available for next working day delivery.
How to Work Out the Size You Need
Measure the maximum length, width and depth of your pond. Pondkeeper’s formula is to add twice the depth to the length and to the width, then allow around 50cm of overlap on every side for edging and anchoring. Its own example is a 2m x 1.5m pond that is 0.6m deep, which needs a liner of roughly 4.2m x 3.7m. Pondkeeper also has a free online pond calculator if you prefer not to do the maths.
Do Not Skip the Underlay
Underlay is cheap insurance for your liner. Pondkeeper points out that 1,000 litres of water weighs a tonne, so even a small pond pushes the liner hard against any sharp stone underneath, while plant roots can grow up from below. Its Basic 60gsm underlay suits small ponds on smooth soil or clay, and costs £16.20 for 3m x 3m. The thicker Best 200gsm fleece is better for larger ponds or stony ground, at £25.20 for 3m x 3m. On very rough ground, Pondkeeper suggests laying compacted sand first. Shop pond underlay at Pondkeeper.
Which Liner Should You Choose?
- Small wildlife pond on a budget: Flexiliner with a long guarantee and Basic underlay.
- Simple rectangular or raised pond: PVC in the 0.5mm grade.
- Irregular shapes, shelves for plants and fish: EPDM rubber with Best underlay.
- Large or heavy-use ponds where toughness matters most: Firestone EPDM.
Conclusion
A good liner and underlay are the foundation of every healthy pond. For most gardens, Flexiliner gives the best value, EPDM offers the best balance of flexibility and strength, and Firestone is the choice when only the toughest will do. Find your pond liner at Pondkeeper.
Frequently Asked Questions
Can a pond liner be repaired?
Yes. Pondkeeper says small tears or punctures can be fixed with a repair patch kit or an adhesive made for the liner material.
Is EPDM better than butyl?
Pondkeeper says EPDM looks and feels almost identical to butyl, costs less and offers better characteristics.
Do I really need underlay?
Pondkeeper strongly recommends it, as it cushions the liner from stones and helps stop roots pushing through.
