- What is a geomembrane?
- What is HDPE?
- What is LLDPE?
- Key differences between HDPE and LLDPE
- Which membrane is best for attenuation tanks?
- Flexibility and installation considerations
- Durability and puncture resistance
- Typical applications for each material
- Frequently asked questions
What Is a Geomembrane?
Geomembranes are impermeable liners used to prevent the movement of water, liquids and contaminants through the ground. They are widely used within civil engineering, Sustainable Drainage Systems (SuDS), attenuation tanks, lagoons, containment systems and environmental protection projects.
Two of the most commonly specified materials are HDPE (High Density Polyethylene) and LLDPE (Linear Low Density Polyethylene).
While both provide an effective waterproof barrier, there are important differences between the two materials.
What Is HDPE?
HDPE stands for High Density Polyethylene.
It is one of the most widely used geomembrane materials within civil engineering due to its excellent strength, chemical resistance and long-term durability.
HDPE geomembranes are commonly specified for: 
- Attenuation tanks
- Stormwater storage systems
- Lagoons
- Environmental containment
- Landfill engineering
- Industrial applications
HDPE is known for its robust performance and resistance to chemicals, making it a popular choice where long-term durability is a priority.
What Is LLDPE?
LLDPE stands for Linear Low Density Polyethylene.
While it offers similar impermeability and chemical resistance to HDPE, it is generally more flexible and easier to conform to irregular shapes and ground conditions.
LLDPE geomembranes are commonly used for:
- Attenuation tank liners
- Decorative and commercial ponds
- Lagoons
- Water features
- Projects requiring greater flexibility
- Complex liner installations
Key Differences Between HDPE and LLDPE
Which Membrane Is Best for Attenuation Tanks?
There is no universal answer.
Both HDPE and LLDPE geomembranes are commonly used within attenuation tank systems.
In many attenuation applications, the decision will depend on:
- Project specification
- Installer preference
- Site conditions
- Membrane thickness
- Detailing requirements
For many standard attenuation tank installations, HDPE remains a popular choice due to its durability and availability.
Where increased flexibility is required, some designers may prefer LLDPE.
Flexibility and Installation
One of the main advantages of LLDPE is flexibility.
LLDPE can be easier to install around complex shapes, corners and penetrations, making it attractive for projects where liner detailing is more complicated.
HDPE is generally stiffer but provides excellent structural performance when installed correctly.
Durability and Puncture Resistance
Both materials offer excellent service life when installed as part of a correctly designed system.
In attenuation tank applications, membrane protection is equally important regardless of material selection.
For this reason, a 300gsm non-woven protection fleece is commonly installed above and below the geomembrane to help protect against puncture damage during installation and backfilling. 
Typical Applications
HDPE Geomembranes
- Attenuation tanks
- Stormwater storage systems
- Environmental containment
- Industrial projects
- Large-scale civil engineering works
LLDPE Geomembranes
- Attenuation tanks
- Ponds and lagoons
- Water features
- Irregularly shaped containment systems
- Projects requiring increased flexibility
Frequently Asked Questions
Is HDPE stronger than LLDPE?
HDPE generally offers greater stiffness and tensile strength, while LLDPE offers increased flexibility.
Which membrane is better for attenuation tanks?
Both materials can be suitable. The correct choice will depend on the project specification, site conditions and installation requirements.
Do both require protection fleece?
Yes. Regardless of membrane type, protection fleece is commonly used to help reduce the risk of puncture during installation.
Can both materials be welded?
Yes. Both HDPE and LLDPE geomembranes can be welded using appropriate installation methods.
Need Help Choosing the Right Geomembrane?
At Drainage & Civils Direct, we supply HDPE geomembranes, protection fleece and installation accessories suitable for attenuation tanks, SuDS and containment projects.
If you’re unsure which membrane is best suited to your project, our team can help identify the most appropriate solution.
If you require assistance selecting the correct specification or need pricing for project quantities, our team is happy to help.
Contact us on 03338803558 or info@drainageandcivilsdirect.co.uk and we’ll point you to the right product and get it delivered fast.
