A Guide To REHAU Pre Insulated Pipe

REHAU pre-insulated pipe provides a flexible and efficient way to transport heating water between heat sources, buildings and plant rooms. Applications range from domestic air source heat pump connections to larger district heating and commercial heat networks.

At Underfloor Store, we supply three REHAU pre-insulated pipe systems: RAUVITHERM, RAUVIPEX and RAUTHERMEX. Each range uses durable PE-Xa carrier pipes, but differences in insulation, construction and flexibility make them suitable for different types of installation.

This guide explains the main differences between the three systems, the choice between UNO and DUO pipe, and the accessories required to complete an installation.

What Is Pre-Insulated Pipe?

Pre-insulated pipe combines one or more carrier pipes with thermal insulation and a protective outer casing. It is commonly installed underground to transfer heating water while helping to minimise heat loss between the heat source and the building.

Typical uses include:

• - Connecting an externally positioned air source heat pump to a property
• - Supplying heating to annexes, workshops and outbuildings
• - Connecting remote plant rooms and energy centres
• - Distributing heat between multiple buildings
• - Creating communal and district heating networks
• - Connecting biomass and other renewable heat sources
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Which REHAU Pre-Insulated Pipe Should You Choose?

The most suitable range will depend on the application, required pipe size, run length, thermal performance requirements, and site conditions.

REHAU RAUVITHERM

RAUVITHERM is a lightweight and highly flexible pre-insulated pipe system. Its flexible, closed-cell PE-X foam insulation and corrugated outer casing make it easier to handle and route, particularly where space is restricted or the pipe must follow changes in direction.

RAUVITHERM is particularly well suited to remote heat pump connections, existing properties and smaller heat networks. It is manufactured at REHAU’s UK plant in North Wales.

RAUVITHERM is ideal for:

• - Air source and ground source heat pump connections
• - Existing and refurbished properties
• - Garages, annexes, workshops and outbuildings
•  Small communal heating systems
• - Smaller district heating networks
• - Biomass heating installations

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REHAU RAUVIPEX

RAUVIPEX is a versatile pre-insulated pipe system developed for low-carbon heat networks and remote heat pump installations. It combines durable PE-Xa carrier pipes with fine-pored PUR foam insulation designed to balance thermal performance and bending flexibility.

The system has a robust corrugated outer jacket and a welded longitudinal watertight barrier. This provides additional protection against moisture entering the insulation if the outer casing becomes locally damaged.

RAUVIPEX is ideal for:

• - Air source and ground source heat pump connections
• - District and communal heat networks
• - Commercial developments
• - Multi-building heating systems
• - Renewable and low-carbon energy projects
• - Underground heating and cooling distribution

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REHAU RAUTHERMEX

RAUTHERMEX is designed for heat networks where high thermal performance is a priority. Its PE-Xa carrier pipes are surrounded by bonded PU foam insulation with a low thermal conductivity, helping to minimise heat loss over longer pipe runs.

The bonded construction also means that below-ground compensation for thermal expansion is not normally required. RAUTHERMEX is available in a broad range of sizes for larger loads and more extensive networks.

RAUTHERMEX is ideal for:

• - District and communal heating networks
• - Long-distance underground heating connections
• - Commercial and residential developments
• - Energy centres and remote plant rooms
• - Multi-building heating schemes
• - Large renewable heating projects

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What Is the Difference Between UNO and DUO Pipe?

REHAU pre-insulated pipe is available in UNO and DUO configurations.

UNO Pre-Insulated Pipe

UNO pipe contains one carrier pipe inside the insulated outer casing. A conventional heating circuit typically requires two UNO pipes: one for the heating flow and another for the return.

UNO can be useful for larger pipe sizes, installations where flow and return need to follow different routes, or projects where separate services are required.

DUO Pre-Insulated Pipe

A DUO pipe contains two carrier pipes within a single insulated outer casing. This enables the heating flow and return to be installed together, reducing the space required and simplifying the route.

For example, a pipe described as 32+32mm DUO contains one 32mm flow pipe and one 32mm return pipe.

Choosing the Correct Pipe Size

Pre-insulated pipe should be sized according to the system design rather than simply matching the connection size on the heat source.

The correct pipe size will depend on factors including:

• - Required heat output
• - System flow rate
• - Flow and return temperatures
• - Total pipe length
• - Available pump pressure
• - Permitted pressure loss
• - Whether the pipe supplies one or several buildings

Choosing a pipe that is too small can cause excessive resistance and reduce system performance. Oversizing may incur unnecessary material and installation costs. Pipe sizing should therefore be confirmed as part of the heating-system design.

REHAU End Caps and Connection Fittings

Compatible accessories are required to protect the pipe insulation and connect the PE-Xa carrier pipe to the heating system.

The REHAU accessories available from Underfloor Store include:

• - RAUTHERMEX rubber end caps
• - RAUVIPEX rubber end caps
• - RAUVITHERM dry end caps
• - Male BSP screw connection fittings
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End caps must be matched to the selected pipe range, UNO or DUO configuration, carrier-pipe size and outer-casing diameter. They should be fitted to exposed pipe ends in accordance with REHAU’s current installation instructions.

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Shop REHAU Pre-Insulated Pipe

Explore our complete range of REHAU RAUVITHERM, RAUVIPEX and RAUTHERMEX pre-insulated pipe, available in UNO and DUO configurations with compatible end caps and connection fittings.

Shop the REHAU pre-insulated pipe range

Please note: Pre-insulated pipe should be selected and installed according to the system design and current REHAU technical guidance. If you are unsure which product or accessory you require, contact our team before ordering.