Product Description

TWPro 125mm Twin Wall Adjustable Pipe 500–880mm Matt Black

Model: 37-125-014

Complete a twin-wall chimney route where a standard fixed pipe will not provide the correct length with the TWPro 125mm Twin Wall Adjustable Pipe 500–880mm. This two-piece insulated chimney section adjusts to provide an effective length between approximately 500mm and 880mm.

The adjustable design helps installers close a measured gap between compatible TWPro components. Therefore, it reduces the need to combine several short fixed lengths when the required chimney height falls between standard pipe sizes.

The component includes a body-soluble ceramic insulation blanket. The installer cuts this blanket to the required size before securing the adjustable section with its supplied locking band.

Please note: This component requires careful on-site adjustment. Measure the required effective length and read the TWPro installation instructions before cutting the insulating blanket or assembling the pipe.

Key Features

• 125mm internal flue diameter
• Adjustable effective length from approximately 500mm to 880mm
• Two-piece adjustable twin-wall construction
• Designed to complete non-standard chimney lengths
• Body-soluble ceramic insulation blanket included
• Insulating blanket can be cut to suit the required effective length
• Locking band included
• No screws required to secure the adjustable section
• Durable matt-black outer finish
• 316L-grade stainless-steel inner casing
• 304-grade stainless-steel outer casing
• Suitable for compatible solid-fuel, gas and oil appliances
• Push-fit TWPro connection system
• Forms part of a T600-rated insulated chimney system
• Compatible with TWPro and corresponding KW Flue components
• Product model: 37-125-014

TWPro 125mm Adjustable Pipe Specification

• Download the TWPro Information Sheet
• Download the TWPro Installation Sheet
• Why We Think TWPro Twin-Wall Flue Is the Best
• Brand: TWPro
• Manufacturer: MI Flues
• Product type: adjustable insulated chimney length
• Nominal internal diameter: 125mm
• Approximate system external diameter: 175mm
• Minimum effective length: approximately 500mm
• Maximum effective length: approximately 880mm
• Adjustment range: approximately 380mm
• Construction: two-piece adjustable pipe
• Inner casing: 0.4mm 316L-grade stainless steel
• Outer casing: 0.4mm 304-grade stainless steel
• Outer finish: high-temperature matt-black coating
• Insulation: mineral wool with adjustable ceramic insulation blanket
• Connection system: push fit with locking bands
• Maximum system temperature class: T600
• Minimum distance to combustible materials: 50mm under the T600 G50 classification
• Product model: 37-125-014

What Is Included?

• 1 x TWPro 125mm Twin Wall Adjustable Pipe
• 1 x adjustable insulating blanket
• 1 x compatible locking band
• Finish: matt black
• Model: 37-125-014

Application

This adjustable chimney length helps complete a TWPro installation when standard fixed sections do not produce the required overall height. For example, an installer can use it to close the remaining gap between a fixed chimney section and a bend, support, roof component or terminal arrangement.

The adjustable pipe can form part of a correctly designed chimney serving compatible appliances such as:

• Wood-burning stoves
• Multifuel stoves
• Other suitable solid-fuel appliances
• Compatible gas appliances
• Compatible oil-fired appliances

Always check the appliance manufacturer’s instructions before ordering. In addition, confirm the required flue diameter, chimney classification, permitted route and support arrangement.

Adjustable Length from 500mm to 880mm

The two-piece construction allows the installer to set an effective length between approximately 500mm and 880mm. As a result, this section provides around 380mm of adjustment within one component.

First, measure the remaining space in the proposed chimney route. Then set the adjustable pipe to the required effective length in line with the TWPro instructions.

The stated dimensions refer to the usable installed length. Therefore, do not select the product solely from the visible distance between two unassembled components. Joint engagement and the position of connected fittings can affect the final measurement.

Why Use an Adjustable Twin-Wall Pipe?

Standard twin-wall pipes come in fixed lengths. However, a complete chimney route may not divide exactly into those standard sizes. Roof levels, bends, wall brackets and appliance positions can all change the final measurement.

This adjustable pipe allows the installer to create the required length without adding several short sections. Consequently, it can reduce the number of visible joints and produce a neater chimney route.

It also gives the installer greater control over the position of nearby supports, bends and roof components. Nevertheless, the complete system must still follow the manufacturer’s support and installation requirements.

Adjustable Insulation Blanket

The component includes a body-soluble ceramic insulation blanket for the adjustable area. The installer cuts the blanket to suit the selected pipe length before completing the assembly.

The insulation must fill the adjustable section correctly. Do not leave gaps, compress it incorrectly or remove more insulation than required because this may affect the thermal performance of the chimney.

Wear suitable protective equipment when handling or cutting insulation. In addition, follow the safety guidance supplied by TWPro and dispose of any waste material responsibly.

How to Measure the Required Length

1. Assemble or position the surrounding chimney components as shown in the installation plan.
2. Measure the remaining effective distance between the two connecting points.
3. Confirm that the measurement falls between approximately 500mm and 880mm.
4. Allow for the required engagement of each push-fit connection.
5. Set the adjustable pipe to the measured effective length.
6. Prepare the insulating blanket in line with the TWPro instructions.
7. Check the measurement again before completing the joint.

If the required distance falls outside the 500–880mm range, select another adjustable length or revise the combination of fixed chimney sections.

Important Cutting Information

The supplied insulation blanket is cut to suit the selected effective length. Do not cut, drill or modify the stainless-steel casings unless the TWPro installation instructions specifically require and permit it.

Cutting a finished metal casing may damage its protective coating, affect the joint and invalidate the product warranty. Therefore, check every measurement before altering any part of the component.

TWPro System Construction

• Inner casing: 0.4mm 316L-grade stainless steel
• Outer casing: 0.4mm 304-grade stainless steel
• Outer finish: matt-black high-temperature coating
• Standard system insulation: dense mineral wool
• Adjustable-area insulation: cut-to-size ceramic insulation blanket
• Joint system: push fit with locking band
• Maximum operating-temperature class: T600

The stainless-steel casings and insulation help retain heat inside the flue while limiting heat transfer to the chimney exterior. This construction also supports stable flue-gas temperatures within a correctly designed installation.

Approvals and System Classification

• HETAS-approved chimney system
• EN 1856-1 T600 N1 W V2 L50040 G50
• EN 1856-1 T200 P1 W V2 L50040 O20
• Suitable for compatible negative-pressure applications up to T600
• Suitable for compatible positive-pressure applications up to T200

The required classification depends on the appliance, fuel and complete chimney design. Therefore, check the designation and compatibility of every component before installation.

Distance to Combustible Materials

The declared minimum distance from the outside of the TWPro insulated chimney system to combustible materials is 50mm under its T600 G50 classification.

Maintain this clearance around the complete adjustable section. Do not fill the air gap with timber, insulation, plasterboard or another combustible material.

The appliance or another part of the installation may require a greater clearance. Therefore, always follow the largest distance stated within the appliance and chimney instructions.

Installation Guidance

• Confirm that the 125mm internal diameter suits the appliance and chimney design
• Check that the required effective length falls between 500mm and 880mm
• Measure the gap carefully before preparing the component
• Allow for the full engagement of each push-fit joint
• Cut and position the supplied insulating blanket as instructed
• Do not leave uninsulated gaps inside the adjustable section
• Push each compatible joint fully together
• Fit and secure every required locking band
• Provide all supports required by the complete chimney design
• Do not allow the adjustable pipe to place excessive weight on the appliance
• Maintain at least 50mm from combustible materials
• Follow the appliance and TWPro installation instructions
• Comply with Building Regulations and all relevant standards

This component forms part of a safety-critical chimney system. Therefore, a suitably competent installer should design and complete the installation. For solid-fuel systems, use a HETAS-registered installer where appropriate.

Supporting the Chimney

An adjustable pipe completes the required length of the chimney route. However, it does not replace structural supports, wall brackets, ceiling supports or base supports.

Plan the support positions before adjusting the pipe. The complete chimney must remain vertical, stable and secure without placing excessive force on the adjustable joint or appliance outlet.

Only use compatible TWPro support components and suitable building fixings for the installation surface.

Compatibility

This adjustable pipe fits the 125mm TWPro and corresponding KW Flue systems only. Other twin-wall chimney brands use different diameters, joint profiles, insulation arrangements and locking methods.

Therefore, do not combine this adjustable pipe with another chimney system unless the manufacturer confirms compatibility in writing.

The stated 125mm measurement refers to the internal flue diameter. Since the TWPro system uses approximately 25mm of insulation around the inner casing, connected twin-wall pipe has an external diameter of approximately 175mm.

Inspection and Maintenance

Inspect the adjustable pipe, locking bands, supports and nearby joints during routine chimney maintenance. Check that the pipe remains correctly positioned and that none of the connected components have moved.

Arrange chimney sweeping at intervals that suit the appliance, fuel and frequency of use. Replace any component that becomes damaged, distorted, badly corroded or insecure.

TWPro Warranty

• 25-year system warranty, subject to the manufacturer’s terms and conditions
• 2-year warranty on the painted finish

Correct product selection, installation, fuel use and maintenance may affect warranty cover. Therefore, keep your proof of purchase and follow all manufacturer instructions.

Why Choose the TWPro Twin-Wall System?

TWPro combines a 316L stainless-steel inner casing with a durable stainless-steel outer casing and high-performance insulation. As a result, it provides a strong and neat chimney system for a wide range of compatible heating appliances.

Its push-fit connections and locking bands also help installers form secure joints. In the UK, the same system may carry the KW Flue name. However, always check the product codes and joint design before combining components.

Why Buy from SNH Tradecentre?

SNH Tradecentre works closely with MI Flues, the supplier behind the TWPro chimney system. Therefore, our team can check technical details, confirm stock and help you select the correct fixed lengths, adjustable pipes, bends and support components.

We also work closely with MI Flues to process orders quickly. As a result, we can often arrange same-day dispatch for eligible in-stock orders placed before the daily cut-off time. Stock and delivery times can vary, so please contact us if your order is urgent.

• Close working relationship with MI Flues
• Fast dispatch on eligible in-stock orders
• Nationwide UK delivery options
• Experienced stove and chimney product advice
• Extensive range of matching TWPro components
• Help checking product and system compatibility
• Secure online ordering
• Support before and after your purchase

If you need help calculating the correct adjustable length or planning your chimney route, contact SNH Tradecentre before ordering.

Frequently Asked Questions

What is the adjustment range?

The pipe provides an effective installed length between approximately 500mm and 880mm. This gives around 380mm of adjustment.

Is this the same as the 350–500mm adjustable pipe?

No. Model 37-125-014 adjusts from approximately 500mm to 880mm. The shorter 350–500mm TWPro adjustable pipe is a different product with model number 37-125-015.

What diameter is the pipe?

The nominal internal flue diameter is 125mm, which is approximately 5 inches. The external diameter of the connected twin-wall system is approximately 175mm.

Does the pipe include insulation?

Yes. The adjustable pipe includes a body-soluble ceramic insulation blanket. The installer cuts and positions this blanket to suit the selected effective length.

Does it include a locking band?

Yes. A compatible locking band comes with the adjustable pipe.

Do I need to use screws?

No screws are required to secure the adjustable pipe itself. Follow the TWPro instructions and use the supplied locking band.

Can I cut the metal pipe?

Do not cut the stainless-steel casings unless TWPro specifically instructs you to do so. The supplied insulation blanket, rather than the finished outer casing, is prepared to suit the required length.

Can I use this pipe with a wood-burning stove?

Yes, it can form part of a compatible TWPro chimney serving a wood-burning or multifuel stove. Always check the appliance instructions and complete chimney design first.

Can it pass through a wall, ceiling or roof?

TWPro is an insulated chimney system, but every building penetration still requires the correct firestop, support, flashing and other approved components. Do not use the adjustable pipe as a substitute for those parts.

How far must it remain from combustible materials?

The declared minimum clearance is 50mm under the system’s T600 G50 classification. Follow any greater clearance required elsewhere in the installation.

Will it fit another brand of twin-wall flue?

No compatibility should be assumed. This component fits the 125mm TWPro and corresponding KW Flue systems. Do not mix chimney brands unless the manufacturer confirms compatibility in writing.

What is the model number?

The model number for the TWPro 125mm Adjustable Pipe 500–880mm is 37-125-014.