Product Description

TWPro 125mm Twin Wall Insulated Adjustable Pipe 350–500mm – Matt Black

Model: 37-125-015

Fine-tune the height of your chimney with the TWPro 125mm Twin Wall Insulated Adjustable Pipe. This telescopic section adjusts from approximately 350mm to 500mm, allowing the installer to complete a flue route when standard fixed lengths do not provide the exact height required.

The pipe combines a 316L-grade stainless-steel inner casing with a strong 304-grade stainless-steel outer casing. In addition, 25mm of mineral-wool insulation helps retain heat within the flue and supports a stable chimney draught.

Its smooth matt-black finish also matches the rest of the TWPro black twin-wall chimney system.

Key Features

• 125mm nominal internal flue diameter
• Adjustable length from approximately 350mm to 500mm
• Provides up to 150mm of adjustment
• Ideal for completing non-standard chimney heights
• Approximate outside diameter: 175mm
• 0.4mm 316L-grade stainless-steel inner casing
• 0.4mm 304-grade stainless-steel outer casing
• 25mm injected mineral-wool insulation
• Durable matt-black powder-coated finish
• Compatible with TWPro and KW Flue systems
• Suitable for compatible solid-fuel, gas and oil appliances
• Maximum operating temperature class: T600
• Declared distance to combustible materials: 50mm
• Product model: 37-125-015

Adjustable from 350mm to 500mm

Standard fixed pipe lengths do not always match the exact height required by an installation. Therefore, this adjustable section lets the installer close a gap between approximately 350mm and 500mm.

The section provides up to 150mm of adjustment. As a result, it can simplify the final connection and reduce the need to redesign the chimney route around fixed-length components.

Always confirm the required installed length before ordering. In addition, allow for every bend, adaptor, support and terminal when calculating the complete chimney height.

When Should You Use an Adjustable Length?

An adjustable length helps complete a straight chimney run where standard 250mm, 500mm or 1000mm sections do not provide the required measurement. For example, it can help align a chimney with a support, roof penetration or connecting component.

However, an adjustable section does not replace a structural support. The complete chimney must still use the correct load-bearing and lateral supports at the positions shown in the TWPro installation guide.

Application

Use this adjustable twin-wall pipe as part of a compatible chimney system for wood-burning stoves, multifuel stoves, gas appliances and oil-fired appliances. Always check the appliance instructions to confirm the required flue diameter and chimney classification.

An approved twin-wall chimney system can pass through walls, ceilings, floors and roofs when installers use the correct fire-stop, support and weatherproofing components. However, every building penetration must follow the TWPro instructions and current Building Regulations.

TWPro 125mm Adjustable Pipe Specification

• Download the TWPro Matt Black information sheet
• View the TWPro installation guide
• Read why we recommend TWPro twin-wall flue
• Product type: adjustable twin-wall insulated flue pipe
• Nominal internal diameter: 125mm
• Approximate outside diameter: 175mm
• Minimum installed length: approximately 350mm
• Maximum installed length: approximately 500mm
• Adjustment range: approximately 150mm
• Inner casing: 0.4mm 316L-grade stainless steel
• Outer casing: 0.4mm 304-grade stainless steel
• Outer finish: matt-black powder coating
• Insulation: 25mm injected mineral wool
• Joint system: TWPro FitSystem
• Fuel compatibility: solid fuel, gas and oil
• Maximum operating temperature class: T600
• Minimum declared distance to combustible materials: 50mm
• System warranty: 25 years, subject to terms and conditions
• Paint-finish warranty: 2 years, subject to terms and conditions

Approvals and Classification

• HETAS-approved chimney system
• CE marked: EN 1856-1 T600 N1 W V2 L50040 G50
• CE marked: EN 1856-1 T200 P1 W V2 L50040 O20

The T600 classification covers operating temperatures up to 600°C under the relevant standard. Meanwhile, the G50 designation declares a minimum distance of 50mm from combustible materials under the stated test conditions.

Installation Guidance

First, measure the gap that the adjustable section must fill. Next, set the pipe within its permitted 350–500mm range. Then secure the adjustable section and adjoining components exactly as shown in the TWPro installation guide.

Keep the section straight and correctly aligned. Furthermore, do not exceed its stated adjustment range, as insufficient overlap may affect the safety and strength of the installation.

Do not cut, drill or modify this insulated pipe. Cutting would damage the tested joint, insulation and protective casing. If the required measurement falls outside the 350–500mm range, choose another suitable component.

Support the chimney independently with the correct load-bearing and lateral supports. Do not allow the adjustable section, appliance or connecting adaptor to carry the chimney’s weight.

This pipe only connects to compatible TWPro and KW Flue components. Do not mix it with another chimney brand unless the manufacturer confirms compatibility in writing.

Clearance from Combustible Materials

Maintain at least 50mm clearance from combustible materials around the chimney, as required by the system’s T600 G50 classification. Combustible materials may include timber, roof battens, furniture and hidden structural components.

Do not assume that plasterboard makes an area non-combustible because timber may sit behind it. Moreover, follow any greater clearance required by the appliance instructions, installation design or Building Regulations.

Maintenance and Inspection

Arrange regular chimney sweeping at intervals that suit the appliance, fuel and frequency of use. During each service, check the adjustable section, joints, locking components and supports for damage or movement.

Also inspect the chimney after severe weather or building work. Replace any component that becomes damaged, distorted, corroded or insecure.

Why Choose TWPro?

TWPro offers a complete insulated chimney system with matching straight lengths, adjustable sections, bends, adaptors, supports, flashings and terminals. Consequently, installers can create a complete chimney route with compatible components from one system.

The 316L stainless-steel inner casing provides strong resistance to corrosion. Meanwhile, the insulated construction helps keep flue gases warm and supports reliable chimney performance.

Why Buy from SNH Tradecentre?

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

Read reviews from SNH Tradecentre customers on Google.

Need help choosing the correct adjustable chimney length? Call SNH Tradecentre on 01843 842727 before ordering.

Frequently Asked Questions

What adjustment does this pipe provide?

The pipe adjusts from approximately 350mm to 500mm. Therefore, it provides up to 150mm of adjustment.

Why would I need an adjustable twin-wall pipe?

An adjustable pipe fills a gap that standard fixed pipe lengths cannot match. It can therefore help complete the chimney at the required height without altering the planned route.

What does the 125mm measurement mean?

It refers to the internal flue diameter. The main insulated pipe has an approximate outside diameter of 175mm.

Can I use it with a wood-burning stove?

Yes, it suits compatible wood-burning and multifuel appliances. Always confirm that the appliance requires a 125mm chimney before ordering.

Can I cut this adjustable pipe?

No. Do not cut or modify it. Instead, set it within its permitted 350–500mm adjustment range or choose another suitable component.

Does it support the weight of the chimney?

No. Install the correct load-bearing supports elsewhere in the system. The adjustable pipe should not carry the chimney’s structural weight.

Can this pipe pass through a wall or ceiling?

Only as part of a correctly designed twin-wall chimney installation that uses the required fire-stop, support and clearance components. Check whether the manufacturer permits an adjustable section at the planned penetration position.

How far must it remain from combustible materials?

The TWPro system carries a G50 designation at T600, which declares a minimum distance of 50mm. Always use any greater clearance required elsewhere in the installation.

Will it fit another twin-wall flue brand?

No, unless the manufacturer confirms compatibility in writing. Different systems can use different dimensions, joint profiles and locking methods.

Who should install the pipe?

A suitably competent person should design and install the chimney. For solid-fuel appliances, consider using a HETAS-registered installer.