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Flexalen 600

Flexible double and single pipe solutions
Flexalen 600 pre-insulated pipes
Flexalen 600 pre-insulated pipes
Flexalen 600 pre-insulated pipes
Flexalen 600 pre-insulated pipes
Flexalen 600 pre-insulated pipes
Flexalen 600 pre-insulated pipes

The Flexalen 600 flexible pre-insulated pipe range is specifically designed to beat today’s most pressing network lifecycle performance and installation challenges. Its unique design and material properties make it a highly versatile network solution for reliable heating, cooling, and potable water supply.

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Flexalen 600 pre-insulated pipes – first-rate material quality 

The Flexalen 600 pre-insulated pipe system consists of a  polybutene (PB-1) medium pipe: a flexible polyolefin material that assures quick and reliable assembly, over 50 year lifetime, while being the best in class for pressure and temperature rating, and energy efficiency.

Enclosing the pipe is a polyolefin-based polyethylene insulation that, thanks to its hydrophobic and closed cell structure, minimizes the risk of water absorption. This ensures the insulation properties of Flexalen 600 are safeguarded over its entire product lifecycle.

The protective HDPE outer casing with UV stabilizers ensures optimal protection against any risk of damage throughout the networks’ entire lifetime, while ensuring flexibility.

Proven sustainability 

Flexalen 600, now the world’s only Cradle to Cradle Certified™ Silver pre-insulated pipe, was developed with the aim of offering an ideal district heating and cooling solution for both engineers, installers and end-users looking for a durable, maintenance-free and quick to install system. The first Flexalen 600 pre-insulated pipe system was already installed in 1983 in Heiligenkreuz (Austria), and has been running smoothly ever since with zero leaks or maintenance issues.

Check out this recent project in Roosendaal, the Netherlands (English subtitles available)


Flexalen 600 is available as a single pipe system (OD25 to 225mm) or a double pipe system (OD25 to 63mm). The polybutene pipe is also available with an oxygen barrier. Flexalen pre-insulated pipes are delivered in coil up to 300m (depending on diameter). Lengths can be customized upon request.

We also offer services to optimize network design and dimensioning, calculation, training, and technical assistance on site.

  • Sustainability

    Cradle 2 Cradle certified – for a circular economy

    Download the certificate in the knowledge center!

  • Health

    Produced without (H)CFC
    Complies to REACH
    Complies to VOC (Volatile organic components)

  • Specificities

    High flexibility

    Usable for both heating and cooling applications

    Safe and secure operation

    Long lifetime expectancy

  • Installation

    Easy quick and safe to weld

  • Service temperature

    Wide temperature range

    Minimum -15°C

    Maximum 95°C

  • Availabilities

    Available in long lengths

    Full range of accessories

    Available with oxygen barrier

    Available in twin or single carrier pipes

    Several insulation thicknesses available for diverse applications

Polybutene-1, ideal for district heating, cooling and potable water networks

Flexalen 600 pre-insulated pipes consist of a flexible polybutene (PB-1) medium pipe, ensuring durable performance in large-scale district heating and cooling networks as well as domestic applications:

  • High flexibility
  • Minimal creep
  • High tensile strength
  • Minimal heat loss
  • Minimal expansion forces
  • Long lifetime (up to 100 years depending on use)
  • Size range from 20 to 125mm in SDR class 11
  • Available with oxygen barrier
  • Smooth internal walls (7 x 10-6 m over lifetime)
  • Less pressure loss, no biofilm or incrustation
  • Allows electrofusion, poly-fusion and butt-fusion welding
  • Cradle to Cradle Certified™ Silver
  • 100% recyclable

Thermaflex insulation foam – high and durable energy performance

Direct extruded polyethylene insulation encloses the pipe, keeping the water absorption coefficient to a minimum thanks to its integrated water vapor barrier and closed cell structure. It is available in 3 thicknesses: compact, standard and large-scale DHC.

HDPE jacket for superior protection

A protective corrugated HDPE outer casing with UV stabilizers ensures high mechanical strength and flexibility throughout the networks’ entire lifetime.

Complex networks mastered by design

Thanks to the unique features of the Flexalen 600 pre-insulated pipe system, many aspects of the network can be optimized to reduce the initial investment and operating costs:

  • Easy welding allows narrow trenches
  • Flexibility eliminates the need for work-arounds, reducing quantity of materials and fittings
  • Low pressure drop allows smaller pipe diameters, faster flow with less pump capacity
  • No network segmentation needed, limiting the number of on-site connections

Our team of network engineers is at your disposal for any technical questions or assistance in dimensioning or route optimization.

Find all the technical details in our product guide in the download section

Flexalen 600 – Optimal installation efficiency

The flexibility, weldability and low weight of Flexalen 600 pre-insulated pipes greatly simplifies and accelerates installation. Electrofusion, poly-fusion and butt-fusion welding techniques ensure durable and record-breaking system welding in respect to ease and speed of installation.

Prefabrication smooths the way

For even faster installation, Thermaflex can deliver fully prefabricated and factory-tested connections. This reduces the amount of on-site welded connections to just 30% of traditional designs. This comes with multiple benefits.

  • Minimize installation risk
  • Reduce handling and trench time
  • Stay on planning and budget
  • Control installation and overhead costs

Comprehensive installation support

  • Installation training
  • Pre-check of design and parts during order
  • On-site installation support
  • Welding training for complex projects
  • Installation manuals

Find all the technical details in the Flexalen product guide in the download section


  Pressure drop PB-pipes PDF 44 KB Preview Download Mail

Pressure drop PB-pipes

Brochures Catalogues

  Flexalen Product Guide PDF 4623 KB Preview Download Mail

The Flexalen Product Guide offers all system, application & technical specifications for all Flexalen product ranges.

  FAQs Polybutene PDF 2492 KB Preview Download Mail

Here you will find answers according the frequently asked quastions about Polybutene.

  Successful in the past - prepared for the future (PBPSA) PDF 1619 KB Preview Download Mail

This brochure is giving an introduction to Polybutene including a review of the performance of Polybutene pressure piping systems in meeting the needs of sustainable building regulations.

  Flexalen - No1 choice for specifiers around the world PDF 817 KB Preview Download Mail

Why is Flexalen the No1 choice for specifiers around the world?

Installation Manuals

  Flexalen instruction: Laying instruction PDF 1936 KB Preview Download Mail

Laying instruction for Flexalen 600, Flexalen 1000+, Straight lenghts and Flexalen Solar.

  Flexalen instruction: Pressure testing PDF 162 KB Preview Download Mail

Pressure testing and pressure test protocol.

Technical Datasheets

  Pre-insulated pipe - Flexalen 600 Short Length Package PDF 311 KB Preview Download Mail
  Pre-insulated pipe - Flexalen 600 Heating/Cooling PDF 278 KB Preview Download Mail
  Pre-insulated pipe - Flexalen 600 Water PDF 240 KB Preview Download Mail
  Pre-insulated pipe - Flexalen 600 FP PDF 300 KB Preview Download Mail

Environmental Certifications

  Cradle to Cradle - Carbon offsetting 2015-2019 PDF 195 KB Preview Download Mail

Thermaflex Isolatie B.V. has offset 290 tonnes of CO2 tooffset 50% of the emissions caused by the production of C2C products (Flexalen 600).

Thermaflex directly invests in emission reduction projects which combine energy, environment and developmental solutions into sustainable business opportunities in developing countries, with the help of the Climate Neutral Group.

  Flexalen 600 - Cradle to Cradle Silver Material Health Certificate PDF 158 KB Preview Download Mail

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