Product Description

TWPro 125mm Twin Wall Insulated Pipe – 250mm Matt Black

Model: 37-125-012

Extend your insulated chimney route with the TWPro 125mm Twin Wall Insulated Pipe in a 250mm length. This short fixed section works well where a 500mm or 1000mm pipe would make the flue route too long.

The pipe measures 250mm overall. However, the joint uses approximately 35mm when it connects to the next component. Therefore, it adds an effective installed length of approximately 215mm to the completed chimney.

Furthermore, the matt-black finish complements wood-burning stoves, black connecting pipes and matching TWPro chimney components. The supplied locking band secures the push-fit joint.

Product at a Glance

• Product type: fixed insulated twin-wall flue pipe
• Nominal internal diameter: 125mm (5 inches)
• Overall length: 250mm
• Effective installed length: 215mm
• Approximate joint overlap: 35mm
• Approximate outside diameter: 175mm
• Inner liner: 0.4mm 316L stainless steel
• Outer casing: 0.4mm 304 stainless steel
• Insulation: 25mm high-density mineral wool
• Finish: matt black
• Joint method: push fit with locking band
• Locking band: included
• Temperature classification: T600
• Minimum distance from combustible materials: 50mm
• Model: 37-125-012
• System warranty: 25 years, subject to conditions
• Paint-finish warranty: 2 years

Key Features and Benefits

• Short fixed section: Helps fine-tune the overall chimney height.
• 215mm installed length: Clearly shows how much height the pipe adds after joint overlap.
• 125mm internal diameter: Connects to matching 5-inch TWPro components.
• Insulated construction: Uses 25mm of high-density mineral wool.
• 316L inner liner: Provides strong resistance to heat and corrosive flue gases.
• 304 outer casing: Protects the insulation and provides a durable outer surface.
• Matt-black coating: Creates a neat appearance on visible internal and external flue routes.
• Push-fit joint: Allows fast connection to matching TWPro components.
• Supplied locking band: Secures the formed joint.
• T600 G50 classification: Suits compatible solid-fuel systems with a 50mm clearance.

Overall Length vs Installed Length

Measurement	Length
Overall pipe length	250mm
Effective installed length	215mm
Approximate joint overlap	35mm

 

The male end enters the adjoining TWPro component during assembly. Consequently, the pipe does not add its full 250mm length to the completed chimney.

Use the 215mm effective length when planning the flue route. In addition, allow for bends, tees, adaptors, adjustable sections, terminals and other joint overlaps.

When Should You Use a 250mm Pipe?

This short pipe can help when a longer fixed section would overshoot the required height or support position. For example, it may help:

• Fine-tune the height of an internal chimney route
• Reach a wall or roof support position
• Adjust the position of an external wall bracket
• Extend the system above a roof flashing
• Complete a route between bends or support components
• Add a short section above a tee or adaptor

However, do not use several short pipes when one longer section would create a simpler route. Fewer joints usually provide a cleaner installation and reduce assembly time.

TWPro Pipe Construction

TWPro uses stainless steel for both chimney casings. The inner liner uses 0.4mm 316L stainless steel, while the outer casing uses 0.4mm 304 stainless steel with a matt-black coating.

A 25mm layer of high-density mineral wool sits between the two casings. This insulation helps retain heat inside the flue and reduces the outside surface temperature.

Furthermore, the fully formed and welded construction provides a strong chimney component for compatible solid-fuel, gas and oil systems.

TWPro 125mm 250mm Pipe Specification

• Download the TWPro matt-black information sheet
• Download the TWPro installation diagram
• Discover why SNH recommends TWPro twin-wall flue
• Product type: rigid fixed twin-wall chimney pipe
• Model and SKU: 37-125-012
• Nominal internal diameter: 125mm (5 inches)
• Approximate external diameter: 175mm
• Overall length: 250mm
• Effective installed length: 215mm
• Approximate joint overlap: 35mm
• Inner casing: 0.4mm 316L stainless steel
• Outer casing: 0.4mm 304 stainless steel
• Outer finish: matt-black high-temperature coating
• Insulation thickness: 25mm
• Insulation type: high-density mineral wool
• Joint method: push fit with locking band
• Locking band: included
• Maximum solid-fuel temperature classification: T600
• Solid-fuel classification: EN 1856-1 T600 N1 W V2 L50040 G50
• Positive-pressure classification: EN 1856-1 T200 P1 W V2 L50040 O20
• Distance from combustible materials at T600: 50mm
• HETAS-approved system
• System warranty: 25 years, subject to conditions
• Paint-finish warranty: 2 years
• Manufacturer: Mi-Flues
• Range: TWPro Matt Black

Understanding the TWPro Classifications

Classification	Typical Meaning
EN 1856-1 T600 N1 W V2 L50040 G50	High-temperature, natural-draught applications with a 50mm combustible clearance
EN 1856-1 T200 P1 W V2 L50040 O20	Lower-temperature, positive-pressure applications with a 20mm declared clearance

The correct classification depends on the appliance, fuel and chimney design. Therefore, the installer must use the class that matches the intended application.

Suitable Appliances

The TWPro system suits compatible solid-fuel, gas and oil appliances. These may include:

• Wood-burning stoves
• Multifuel stoves
• Wood-pellet appliances
• Suitable gas appliances
• Gas coal-effect fires
• Compatible oil-fired appliances
• Other appliances approved for the relevant TWPro classification

Always check the appliance instructions before ordering. The manufacturer will state the required flue diameter, temperature class, pressure class and chimney arrangement.

Internal and External Chimney Routes

You can use TWPro on suitable internal or external chimney routes. For example, the system may travel vertically through the property or pass through an external wall before continuing upwards.

For internal installations, use the required supports, fire stops, ventilation components and finishing plates. For external installations, use suitable wall supports, brackets, weathering parts and terminals.

The exact components will depend on the building, appliance and chimney design. Therefore, plan the complete route before ordering individual pipe sections.

Passing Through Walls, Ceilings and Roofs

TWPro is an insulated chimney system, so installers can use it for suitable building penetrations when they follow the manufacturer’s instructions.

However, the pipe alone does not complete a safe penetration. You must also use the correct:

• Wall sleeves
• Fire-stop plates
• Ceiling supports
• Ventilated fire stops where required
• Roof supports
• Flashings and storm collars
• Finishing plates

Do not place single-wall stove pipe through a wall, ceiling, floor or roof. Change to the suitable insulated TWPro system before reaching the building structure.

Installation and Joint Direction

Inspect the pipe before installation. Do not use it if the casings, joint or coating show signs of serious damage.

Fit the pipe in the direction shown in the TWPro installation instructions. Push the formed connection fully into the adjoining component. Next, position the supplied locking band around the joint and secure it correctly.

Check that the internal flue path remains continuous and that the joint cannot separate. Also, keep the pipe vertical or at the angle permitted by the complete system design.

Locking Band and Structural Support

The locking band secures the connection between two TWPro components. However, it does not carry the full weight or sideways load of the chimney.

Therefore, use the correct wall supports, ceiling supports, roof supports and wall brackets. Follow the manufacturer’s stated maximum distances between supports.

Do not allow the stove outlet or single-wall adaptor to carry the weight of the complete chimney.

Distance from Combustible Materials

The T600 G50 classification requires at least 50mm between the outside of the TWPro pipe and combustible materials.

Combustible materials may include:

• Timber studs and roof structures
• Wooden beams and joists
• Furniture and cupboards
• Insulation materials
• Decorative wall coverings
• Timber hidden behind plasterboard

Maintain this clearance continuously around the pipe. Do not fill the 50mm air space with insulation, sealant or other material unless the tested installation detail specifically permits it.

The appliance or another component may require a greater clearance. If the requirements differ, always follow the greatest stated distance.

Can You Cut This Pipe?

Do not cut a fixed twin-wall chimney pipe. Cutting could damage the formed joints, inner liner, insulation and outer casing. It would also prevent the supplied locking band from securing the connection correctly.

Instead, choose a suitable combination of fixed and adjustable TWPro components to achieve the required chimney height.

Inspection and Maintenance

Inspect the pipe, locking bands and supports regularly. Check for:

• Loose or incorrectly fitted joints
• Movement in the chimney
• Damage to the matt-black coating
• Corrosion or staining
• Signs of overheating
• Signs of escaping combustion products

Arrange chimney sweeping and appliance servicing at intervals that suit the fuel and frequency of use. Furthermore, make sure the complete chimney provides suitable access for inspection and cleaning.

Only clean the outside after the chimney has cooled fully. Use a soft, dry or slightly damp cloth. Avoid abrasive pads and strong chemicals because they may damage the black finish.

Important Safety Information

• Use this pipe only with compatible 125mm TWPro components.
• Use the 215mm effective length when planning the chimney.
• Push every joint fully together.
• Secure the joint with the supplied locking band.
• Maintain at least 50mm from combustible materials for T600 applications.
• Do not fill the required clearance space unless an approved detail allows it.
• Use the correct components at walls, ceilings, floors and roofs.
• Support the chimney independently from the appliance.
• Follow the appliance and TWPro installation instructions.
• Comply with current Building Regulations and relevant standards.
• Use a suitably competent installer.

Why Choose TWPro?

TWPro provides a high-quality insulated stainless-steel chimney system for solid-fuel, gas and oil installations. Its push-fit joints and locking bands help installers create a secure chimney route with a clean outer profile.

Furthermore, the T600 G50 classification allows a 50mm clearance around the correctly installed insulated system. This compact clearance can help when planning internal and external chimney routes.

The matt-black finish complements black stoves and connecting pipes. Therefore, it works particularly well where part of the chimney remains visible inside the room.

Why Buy from SNH Tradecentre?

• Specialist stove, chimney and flue-system supplier
• Extensive range of matching 125mm TWPro components
• Practical flue-planning advice from an experienced team
• Nationwide UK delivery options
• Secure online ordering
• Trade counter in Birchington, Kent
• Support before and after your purchase

Need help working out which TWPro pipe lengths you require? Call the SNH Tradecentre team on 01843 842727 before ordering.

You can also read SNH Tradecentre customer reviews on Google.

Frequently Asked Questions

What is the overall length of this pipe?

The overall length is 250mm.

What is the effective installed length?

The pipe adds approximately 215mm to the completed chimney after allowing for the joint overlap.

Why does a 250mm pipe only add 215mm?

Approximately 35mm enters the adjoining component to form the push-fit connection.

What is the internal diameter?

The nominal internal diameter is 125mm, which equals approximately 5 inches.

What is the outside diameter?

The outside diameter is approximately 175mm because the pipe includes 25mm of insulation and an outer casing around the 125mm inner liner.

Does the pipe include a locking band?

Yes. The pipe comes with the locking band required to secure its TWPro joint.

Can I use it with a wood-burning stove?

Yes, it suits compatible wood-burning and multifuel appliances when installed as part of a correctly designed 125mm TWPro system.

Can this pipe pass through a wall or ceiling?

TWPro can form part of a suitable building penetration. However, you must also use the correct wall sleeve, fire stops, supports and finishing components shown in the installation instructions.

How far must it remain from combustible materials?

The T600 G50 classification requires at least 50mm between the outside of the pipe and combustible materials.

Can I cut the pipe?

No. Cutting would damage the formed joints, insulation and casings. Use compatible fixed or adjustable TWPro components instead.

What does T600 mean?

T600 means the system has a nominal maximum continuous flue-gas temperature classification of 600°C for the relevant installation class.

What warranty does it include?

SNH lists a 25-year system warranty and a two-year warranty on the paint finish. The manufacturer’s installation, fuel and maintenance conditions will apply.