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Box Welded Pond Liners

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Measure the greatest width, greatest length and maximum depth. To calculate the size of liner you need.

Custom-made to fit your requirements

Perfect for Koi and ornamental ponds

No unsightly creases or folds in your pond

Lead time: 10 - 14 working days

Quality Box Welded Pond Liner

Our box welded liners are the perfect solution for formal, ornamental, swimming or Koi ponds, where the sides of the pond are vertical and the base is flat. Every one of our box welded liners is prefabricated in our factory, to your bespoke requirements. Known commonly as fish pond liners, box welded to individual shapes, a box pond liner can be the perfect solution for the pond in your garden. 

Why should I choose a made-to-measure, bespoke liner?

For formal ponds, either above or below ground, a tailor-made pond liner will fit the exact dimensions of your pond. When the liner is delivered to you, you simply unfold it and slip it snugly into place. It’s very quick and easy to install. A simple fish pond liner alternative to the standard liner.

Once in the pond, box welded pond liners do not have any unsightly folds or creases that need to be hidden as you would get if using a flat sheet liner. Box-welded pond liners are also manufactured with a flange around the top that can be laid under paving flags to secure the top of the liner.

All our tailored liners are made from 0.75mm or 1.00mm SealEco EPDM and heat welded (vulcanised) in our factory to ensure maximum strength and endurance of the liner.


Are box-welded liners suitable for Koi ponds?

Yes! We have completed many Koi pond lining installations in the past (even some Koi farms) using a box weld liner. Using a bespoke liner in a formally shaped pond, provides the perfect habitat for Koi and other larger fish varieties because the whole area of the pond has a greater depth compared to a natural pond which will get shallower near the edges.

The SealEco EPDM that we use for all our made-to-measure liners is certified non-toxic, so it will have no impact on any Koi, other aquatic life, or plants you choose to put in your pond. It is also unaffected by UV, temperature fluctuations or frost, so you can be safe in the knowledge that your liner won’t become brittle or crack.

For more information regarding our Koi ponds and fish pond liner solutions, please submit an enquiry today or contact our knowledgeable team on:01225 632444.

Please note: Current lead times are 10-14 working days from receipt of order.

Size Guide

We have been fabricating box welded liners for over 50 years, and have done everything from simple circular or rectangular shapes, to ponds with multiple steps, varying wall angles and separate sections.

In order to supply the best liner for you, every liner is tailored to fit your specific requirements. For simple shapes, you can provide the measurements for the length, width and depth required. For more complicated designs, a drawing or template may be required to ensure the liner is customised to fit.

Where you have multiple connected formal ponds or rills, we can supply each section as a separate box liner that would be joined together on site.

To get the best out of your bespoke liner, we would recommend that all pond or lake liners are installed with a good quality pond underlay to provide protection from stones and roots. We supply AquaSHIELD protective matting in both 200gsm and 275gsm.


Are Box-Welded Liners Expensive?

Box welded liners do cost more than a flat sheet liner because they take additional fabricating time to weld the joints, but they are not as expensive as you might think. As an example, we have shown an indicative price for SealEco 0.75mm EPDM for a square and circular box welded liner (including a 150mm flange).


1.5m (W) x 1.5m (L) x 0.5m (D) 1.5m (Diameter) X 1.0m (Deep)
Square Box Welded Liner: £212.40 (inc VAT) Circular Box Welded Liner: £242.40 (inc VAT)

Technical Specification


Brand SealEco GreenSeal
Thickness 0.75mm or 1.00mm
Max Size (supplied as a single sheet) Depends on shape
Other Sizes Available Yes, please contact us on 01225 632444 with your requirements


Weight (per m2) 1.00kg for 0.75mm; 1.25kg for 1.00mm
Elasticity 300% elongation (allowing for adjustment/movement of the surface it is laid on)
Life Span 40 years
Joining Possible Onsite Yes
Puncture Resistance Good
Aquatic, plant & human safe Yes

Koi Ponds

Ornamental Ponds

Formal Ponds

Swimming Ponds

Water Features



All our liners are sent out with full installation instructions. You can also find guides to building and installing your liner in our Help & Guides: How To section.

For larger projects, we can assist with installation if required. This can either be undertaken by us or one of our partners. For more information, please see our Pond Liner Installations section or contact us.

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