Product Description

TWPro 125mm Single Wall to Twin Wall Adaptor – Matt Black

Model: 37-125-001

Connect a compatible 125mm single-wall stove pipe to a 125mm TWPro insulated chimney system with this TWPro Single Wall to Twin Wall Adaptor. The adaptor creates the correct transition from the visible connecting flue near the appliance to the insulated twin-wall chimney above.

The lower connection accepts a compatible 125mm single-wall or vitreous enamel pipe. Meanwhile, the upper connection joins directly to the TWPro 125mm twin-wall system and uses the supplied locking band.

Furthermore, the matt-black outer finish creates a neat transition between black stove pipe and matching TWPro black chimney components.

Product at a Glance

• Connects 125mm single-wall pipe to 125mm TWPro twin wall
• Suitable for compatible vitreous enamel stove pipe
• 125mm nominal internal flue diameter
• Matt-black outer finish
• 316L stainless-steel inner liner
• 304 stainless-steel outer casing
• 25mm high-density mineral-wool insulation
• Push-fit TWPro connection with locking band
• Locking band included
• Suitable for compatible solid-fuel, gas and oil appliances
• Solid-fuel temperature classification: T600
• TWPro combustible clearance: 50mm
• Model: 37-125-001
• EAN: 5060795861441
• System warranty: 25 years, subject to conditions
• Paint-finish warranty: 2 years

Key Features and Benefits

• Correct system transition: Connects a compatible single-wall flue to TWPro insulated twin wall.
• Matching diameter: Maintains a nominal 125mm internal flue diameter.
• Matt-black finish: Complements black stove pipe and matching TWPro components.
• Strong inner liner: Uses 0.4mm 316L stainless steel for resistance to heat and corrosion.
• Durable outer casing: Uses 0.4mm 304 stainless steel with a black coating.
• Insulated construction: Contains a 25mm layer of high-density mineral wool.
• Secure connection: Uses the TWPro push-fit joint and locking-band system.
• T600 classification: Suits compatible high-temperature solid-fuel applications.
• 50mm twin-wall clearance: Offers a compact clearance where the certified TWPro section applies.
• Long warranty: Includes a 25-year system warranty, subject to the manufacturer’s conditions.

What Does This Adaptor Do?

A stove installation often starts with single-wall connecting pipe close to the appliance. However, the flue must change to an insulated chimney system before it passes through a wall, ceiling, floor, roof or concealed area.

This adaptor creates the transition between those two systems. The lower end connects to compatible 125mm single-wall stove pipe, while the upper end accepts matching TWPro 125mm insulated flue.

As a result, the installer can continue the chimney route with TWPro pipes, bends, supports, fire stops, flashings and terminals.

Where Should You Use the Adaptor?

Use the adaptor at the planned change from single-wall connecting flue to TWPro insulated chimney. The exact transition point will depend on:

• The appliance manufacturer’s instructions
• The route of the chimney
• The position of combustible materials
• The required support arrangement
• Current Building Regulations
• The TWPro installation instructions

The adaptor does not allow single-wall pipe to pass through part of the building structure. Instead, it provides the connection point where the installation changes to the suitable insulated system.

Compatible Single-Wall Flue Pipe

The lower end can connect to a compatible 125mm single-wall flue, including suitable vitreous enamel stove pipe. However, different brands may use different joint profiles and dimensions.

Therefore, do not select the product by nominal diameter alone. Confirm that the chosen single-wall pipe fits the adaptor correctly and follows the required male-to-female joint direction.

If you plan to connect VIT-Smooth or another stove-pipe range, check compatibility before ordering. The SNH Tradecentre team can help confirm the correct transition components.

TWPro Construction

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

Between these casings, a 25mm layer of high-density mineral wool reduces the temperature on the outside of the chimney. Consequently, the certified TWPro section can sit closer to combustible materials than standard single-wall stove pipe.

The components use fully formed joints and a locking band to create a secure connection. In addition, the smooth outer profile gives the completed chimney a clean appearance.

TWPro 125mm Adaptor Specification

• Download the TWPro matt-black information sheet
• Download the TWPro installation diagram
• Product type: single-wall to twin-wall adaptor
• Model and SKU: 37-125-001
• EAN: 5060795861441
• Nominal internal diameter: 125mm (5 inches)
• Single-wall connection: 125mm
• Twin-wall connection: TWPro 125mm
• Inner casing: 0.4mm 316L stainless steel
• Outer casing: 0.4mm 304 stainless steel
• Outer finish: matt-black high-temperature coating
• Insulation: 25mm 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
• TWPro 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 Two Classifications

The TWPro system carries two classifications for different operating conditions:

Classification	Typical Meaning
EN 1856-1 T600 N1 W V2 L50040 G50	High-temperature, natural-draught applications with a 50mm distance from combustible materials
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 full chimney design. Therefore, the installer must use the classification that matches the intended application.

Suitable Appliances

The adaptor suits compatible solid-fuel, gas and oil appliances when used as part of a correctly designed TWPro system. These may include:

• Wood-burning stoves
• Multifuel stoves
• 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.

Installation Guidance

First, confirm that both systems have a nominal internal diameter of 125mm. Next, check that the single-wall pipe has the correct joint profile for the lower connection.

Push the first TWPro component fully into the upper connection. Then fit and close the supplied locking band around the joint. The locking band secures the two TWPro components together.

Install the adaptor in the correct direction and keep the flue-gas path continuous. In addition, support the twin-wall chimney with the brackets and supports specified in the TWPro instructions.

Do not expect the adaptor or stove outlet to carry the full weight of the chimney. Instead, transfer the load to suitable wall, ceiling or roof supports.

Important Clearance Information

The T600 classification gives the insulated TWPro section a minimum distance of 50mm from combustible materials. Measure this clearance from the outside surface of the twin-wall component.

However, this adaptor connects to single-wall stove pipe. Single-wall pipe normally requires a much greater clearance from combustible materials. Therefore, maintain the clearance required by each component and always follow the greatest distance where their clearance zones overlap.

Combustible materials may include:

• Timber studs and roof structures
• Wooden beams, shelves and mantels
• Furniture and curtains
• Decorative wall coverings
• Timber hidden behind plasterboard

Plasterboard does not automatically make a wall non-combustible. For example, it may cover a timber frame. Check the complete construction before confirming the transition position.

Passing Through Walls and Ceilings

Do not pass the single-wall pipe or the uninsulated connection through a wall, ceiling, floor, roof or concealed space.

The system must change to suitable insulated twin wall before reaching the building penetration. The required distance between the adaptor and the penetration will depend on the manufacturer’s installation instructions and the surrounding materials.

Use the correct TWPro fire stops, finishing plates, supports and weathering components for the planned route.

Locking Band and Joint Security

The TWPro connection uses a push-fit joint with a locking band. Push the components fully together before fitting the band.

Next, position the locking band correctly around the formed joint and secure it as the manufacturer directs. Check that the joint cannot separate and that the chimney remains correctly aligned.

The locking band secures the joint, but it does not replace the required structural supports. Therefore, fit all wall brackets, ceiling supports and roof supports shown in the installation design.

Can the Adaptor Be Cut?

Do not cut or alter the adaptor unless the manufacturer specifically permits the modification. Cutting could damage the connection profiles, insulation, coating or stainless-steel casings.

Instead, use compatible straight or adjustable sections to achieve the required chimney height. This approach keeps the tested joints and factory finish intact.

Inspection and Maintenance

Inspect the adaptor, locking band and adjoining pipework regularly. Check for:

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

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

Only clean the outer surface after the chimney has cooled fully. Use a soft, dry or slightly damp cloth and avoid abrasive products.

Important Safety Information

• Use the adaptor only with compatible 125mm components.
• Check compatibility between the single-wall pipe and adaptor before installation.
• Use the supplied locking band on the TWPro joint.
• Maintain at least 50mm from combustibles around the certified T600 twin-wall section.
• Follow the greater clearance required by the adjoining single-wall pipe.
• Do not pass single-wall pipe through building structures.
• Support the chimney independently from the stove and adaptor.
• 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 an insulated stainless-steel chimney system for solid-fuel, gas and oil installations. Its push-fit joints and locking bands help installers build 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 version complements black stoves and connecting pipes. Therefore, it works particularly well where part of the twin-wall 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
• Matching vitreous enamel stove-pipe options
• Practical 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 confirming the correct transition from your stove pipe to TWPro twin wall? Call the SNH Tradecentre team on 01843 842727 before ordering.

You can also read SNH Tradecentre customer reviews on Google.

Frequently Asked Questions

What does this adaptor connect?

It connects a compatible 125mm single-wall or vitreous enamel stove pipe to the 125mm TWPro insulated twin-wall chimney system.

Is the diameter 125mm on both sides?

The nominal internal flue diameter remains 125mm. However, the outside of the twin-wall section is larger because it includes insulation and an outer casing.

Does the adaptor include a locking band?

Yes. The adaptor includes the locking band required to secure the TWPro joint.

Can I connect any brand of 125mm stove pipe?

Not necessarily. Products with the same nominal diameter can use different joint profiles. Therefore, confirm compatibility before ordering.

Can I connect VIT-Smooth stove pipe?

The adaptor can connect compatible 125mm vitreous enamel pipe to TWPro twin wall. However, check the precise joint compatibility and orientation before ordering.

Can the adaptor pass through a ceiling or wall?

No. Position the transition so the suitable insulated TWPro system passes through the building structure. Do not place the single-wall connection inside a wall, ceiling, floor, roof or concealed space.

What clearance does the TWPro section need?

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

Does the 50mm clearance also apply to the single-wall pipe?

No. The adjoining single-wall pipe may need a much greater clearance. Follow its product classification and the appliance instructions.

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.

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 T600 TWPro chimney system.

What materials does the adaptor use?

It uses a 0.4mm 316L stainless-steel inner liner, a 0.4mm 304 stainless-steel outer casing and 25mm of high-density mineral-wool insulation.

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, maintenance and registration conditions will apply.