Preformed vs Flexible Pond Liners: DIY Guide to Choosing the Right Type

Preformed vs Flexible Pond Liners: DIY Guide to Choosing the Right Type

The key to any successful pond is a durable and reliable pond liner

It’s not enough to simply dig a hole in the ground and fill it with water; a waterproof liner is a must-have

For backyard pond enthusiasts, there are two main do-it-yourself options for pond liners: performed ponds and flexible liners. Both types have their place in pond creation but it’s important to understand their differences. 

 

Preformed Pond Liners: Benefits, Features, and Options

Preformed ponds are commonly made from high-density polyethylene (HDP), a plastic molded into a semi-ridged shape that forms the basis of the pond. HDP is known for its durability, resistance to ultraviolet (UV) damage, and often comes with a lifetime warranty

These preformed ponds come in various shapes, including round, rectangular, and free-form, and some feature built-in shelves for potted plants. 

Their depth and size can vary greatly, with preformed ponds holding between 50 to 400 gallons of water. 


Key features to consider when choosing a preformed pond:

  1. Cost: The price is determined by the size of the pond and the complexity of the preformed shape/design.
  2. Weight: Preformed ponds are relatively lightweight making them easy to transport. However, larger models may require two people for moving.
  3. Flexibility: Designed to have some flexibility, the rigid plastic needs proper support (sides and bottom). Without it, the pond might buckle under stress.  
  4. UV Resistance: Preformed ponds are treated to resist UV damage, ensuring longevity and stability under sunlight. 

 

Flexible Pond Liners: Versatile Choices for Custom Ponds

Flexible pond liners serve as adaptable waterproof barriers and are available in materials such as:

  • Polyvinyl Chloride (PVC) plastic sheeting
  • Ethylene Propylene Diene Monomer (EPDM) synthetic rubber
  • High-Density Polyethylene (HDPE) polymer
  • Low-Density Polyethylene (LLDPE) liner

These liners prevent water from seeping into the soil beneath the pond. 

A key specification of flexible pond liners is their thickness, measured in mils (a thousandth of an inch). For instance, a 20-mil liner is 0.020 inches thick. Ornamental ponds typically use liners that are 18-20-mil thick, while professional-grade liners are around 45-mil thick, offering greater thickness and durability. 

A major cause of these liners’ breakdown is exposure to UV light, which can cause degradation over time. 

Here’s a breakdown of the characteristics of each flexible pond liner material: 

 

PVC Pond Liners: Affordable and Lightweight Options

  • Cost: PVC liners are more affordable than other types, making them a popular choice for budget-conscious pond owners. 
  • Weight: PVC liners are lighter in weight than EPDM and HDPE (read below), simplifying handling and maneuvering during installation.  
  • Flexibility: PVC’s flexibility allows it to fit into diverse pond shapes, especially advantageous for ponds with unique and irregular contours.  
  • UV Resistance: PVS liners have good UV resistance but might not be as durable in prolonged sunlight exposure as EPDM. Over time, UV exposure causes some degradation in PVC liners. 
  • Puncture Resistance: PVC liners are fairly resistant to punctures.
  • Lifespan: They generally have a shorter lifespan compared to other flexible pond liner materials.  

 

EPDM Liners: Premium, Durable Choice for Long-lasting Ponds

  • Cost: EPDM liners are considered a premium option and are priced higher than PVC liners.  
  • Weight: These liners are heavier than PVC and HDPE liners, which can make installation a bit more challenging and increase shipping costs. 
  • Flexibility: EPDM liners are flexible, adapting well to various pond shapes.  
  • UV Resistance: EPDM material is renowned for its excellent UV resistance. It can withstand prolonged exposure to sunlight without significant degradation.
  • Puncture Resistance: EPDM has a reputation for fair puncture resistance.
  • Lifespan: These liners typically have a longer lifespan compared to PVC liners. 

 

HDPE Pond Liners: Combining Durability with Flexibility

  • Cost: HDPE liners are more costly than PVS but offer long-term durability (which may justify the investment). 
  • Weight: HDPE liners are heavy. While the weight contributes to their higher durability, handling, and installation can be more challenging, especially for larger ponds.
  • Flexibility: HDPE liners are flexible but due to the thickness of the material, it may require extra effort to work around contours like shelves. 
  • UV Resistance: Renowned for their excellent UV resistance, HDPE liners withstand prolonged exposure to sunlight without significant degradation. 
  • Puncture Resistance: HDPE liners are known for fair puncture resistance.
  • Lifespan: HDPE liners typically have a longer lifespan compared to other materials described above. 

 

LLDPE Liners: Soft and Malleable Solutions for Complex Ponds  

  • LDPE liners share similar qualities to HDPE (see above) but are softer, making them easier to mold around tight corners. 

Choosing the Best Pond Liner for Your Needs

Preformed liners simplify the installation of small ponds; just ensure the hole has proper leveling and support from the sides and bottom. 

PVS is an economical and lightweight choice, often found in budget pond kits that are sold online and shipped directly to you. The low-grade PVC commonly used in pond kits will not last as long as EPDM and HDPE, so we recommend you always use protective pond underlayment material under PVC to at least protect against punctures by roots and rocks. 

EPDM, HDPE and LLDPE are soft and flexible, suitable for shaping around complex pond features (e.g. shelves, curved sides of the pond). The use of underlayment is also recommended, especially near trees or rocky terrain. 

For durability, professional pond installers recommend 45-mil EPDM liner for the toughest, long-lasting performance. However, many successful DIY ponds use 20-mil liners. Selecting the best liner within your budget is crucial, as it forms the foundation of your pond’s success. 


beautiful pond with water lillies and fountain

Top Pond Liner Options for Enhanced Pond Durability and Aesthetics

Preformed Pond Liners:

  • Simplifies and streamline the process of installing small ponds. 
  • Their installation requires precise hole size for proper leveling and support. 

PVC Liners: 

  •   Economical and lightweight solution. Easy to use. 
  •   Commonly found in budget-friendly pond kits sold online.
  •   Low-grade PVC used in these kits may not be as durable as EPDM or HDPE liners.
  •   Always use protective pond underlayment material under PVC to guard against punctures.

 EPDM, HDPE, LLDPE Liners:

  •   EPDM, HDPE, and LLDPE are soft, flexible, and durable.
  •   Ideal for contouring around pond features like shelves and curved sides of the pond.
  •   Often recommended by professional pond builders for their longevity.
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