HDPE Pond Liner UK | Lifetime Guarantee | Includes Free Underlay | 0.35mm

HDPE Pond Liner with Lifetime Guarantee and Free Underlay

If you are building a garden pond, a wildlife pond or a fish pond and you want one liner that you never have to think about again, this is the one to look at. It is a 0.35mm black HDPE (high-density polyethylene) pond liner that carries a lifetime guarantee against UV damage, and every size comes with a protective underlay included in the price. It is sold in 34 pre-cut sizes from 2m x 2m to 12m x 18m, so you can match it to a small patio pond or a large garden feature without joining sheets.

Why it works

Sunlight is what usually ends a liner

The part of a liner that fails first is rarely the bit under the water. It is the strip around the edge that sits in the sun, between the waterline and the coping, where ultraviolet light slowly makes cheaper plastics brittle. This liner is made to resist sunlight for extended outdoor use, and the lifetime guarantee is specifically against UV damage, so the exposed margins are covered for as long as you own the pond.

Tough, but still easy to shape

At 0.35mm the sheet is strong enough to stand up to the weather yet light and flexible enough to fold into shelves, corners and gentle curves. It is lighter than rubber, so it is easier to carry, unfold and pleat neatly; on larger sizes a second pair of hands helps.

Underlay protects what the guarantee does not

The guarantee is against UV damage. A stone, a sharp root or a dropped tool is a different kind of risk, and that is what the included underlay is for. Laid on the prepared base first, it cushions the liner and spreads point loads, which is the single biggest thing you can do to help a liner last.

• Lifetime guarantee against UV damage
• Underlay included with every size
• 0.35mm HDPE: strong, light and flexible
• Suitable for koi, wildlife and ornamental ponds

Where it's used

Typical jobs include new informal garden ponds with planting shelves, wildlife ponds with a shallow beach edge, formal rectangular ponds framed with slabs, goldfish and koi ponds, and replacing a tired or leaking liner in an existing hole. Contractors use the larger sizes where a single sheet with no joins matters.

Specifications

Choosing the right size

Measure the longest length, the widest width and the deepest point of the pond, then work out each direction separately:

Liner length = pond length + (2 x maximum depth) + 0.6m
Liner width = pond width + (2 x maximum depth) + 0.6m

The extra 0.6m gives you a 30cm overlap on every edge for anchoring under slabs or stone. Round up to the next size available; sizes work either way round. For example, a 3m x 2m pond that is 0.6m deep needs at least 4.8m x 3.8m, so the 4m x 6m size is the one to choose. A 4m x 3m pond at 0.75m deep needs 6.1m x 5.1m, which points you to 6m x 7m. If you are between two sizes, go up. Not sure? Use the pond liner size calculator.

Installation, use and care

Dig the hole with shelves where you want marginal plants, then remove stones and roots and firm the base. Lay the included underlay first, then unfold the liner on a warm day so it relaxes, and centre it over the hole. Start filling with water slowly, easing the liner into the corners and folding neat pleats as it settles. Once the pond is full, trim the edge leaving the 30cm overlap and bury or bed it under your coping. Keep sharp tools away from the sheet.

Frequently asked questions

What does the lifetime guarantee cover?

It is a lifetime guarantee against UV damage, which is the main cause of liners becoming brittle and cracking around the sunlit edges. Punctures and physical damage are a separate risk, which is why an underlay is included and why the base should be cleared of stones and roots.

Is the underlay really included with every size?

Yes. Every size in this listing comes with a protective underlay at no extra cost. Lay it on the prepared base before the liner goes in.

Is this liner safe for fish?

It is suitable for koi, wildlife and ornamental ponds.

How is this different from your 40-year HDPE liners?

It is the same family of HDPE liner, with the guarantee extended to lifetime against UV damage and the underlay included. If you want the longest cover on an HDPE liner, this is the one to choose.

Ordering

Pick your size from the list; each one is a single pre-cut sheet supplied with its underlay. Because liners are supplied cut to size, please double-check your measurements with the formula above before you order, and see our returns policy for details. If you are unsure which size suits your pond, our team is happy to help you check it.

Helpful guides

• Pond liner sizing: measure and order the right size
• Pond liner installation: all guides
• Pond liner materials compared
• HDPE pond liners