Product Description

TWPro 125mm Twin Wall Insulated 45 Degree Bend – Matt Black

Model: 37-125-031

Create a substantial change of direction in a 125mm insulated chimney with the TWPro 45 Degree Twin Wall Bend. This fixed two-segment bend moves the chimney route by 45° while maintaining a continuous insulated flue.

Installers can use one bend for a directional change or combine two matching bends with a straight pipe to create an offset. Therefore, the component offers a practical way to route a chimney around joists, roof structures, eaves and other obstacles.

The bend features a 316L stainless-steel inner casing, high-density mineral wool insulation and a matt-black 304-grade stainless-steel outer casing. In addition, the push-fit FitSystem joints and locking bands create secure connections to matching TWPro components.

Product at a Glance

• 125mm nominal internal flue diameter
• Fixed 45° chimney bend
• Two-segment construction
• Creates a substantial change in chimney direction
• Use two matching bends to form an offset
• Suitable for internal and external chimney routes
• 316L stainless-steel inner casing
• 304-grade stainless-steel outer casing
• High-temperature matt-black external coating
• 25mm high-density mineral wool insulation
• Push-fit FitSystem connections
• Locking-band joint system
• Suitable for compatible solid-fuel, gas and oil appliances
• HETAS approved and CE marked
• T600 temperature classification
• G50 soot-fire resistance classification
• 50mm declared distance to combustible materials
• Product model: 37-125-031

What Is a 45 Degree Twin Wall Bend Used For?

A chimney should rise as straight and vertically as possible. However, joists, rafters, eaves and other parts of the building can sometimes block the ideal route.

This 45° bend creates a larger change in direction than the TWPro 15° and 30° bends. As a result, it can produce more sideways movement over a shorter distance.

A second matching bend can return the chimney to a vertical or parallel route. Therefore, installers often use 45° bends in pairs to form a calculated chimney offset.

Key Features

• Creates a fixed 45° change in direction
• Useful for larger chimney offsets
• Two-segment design provides a controlled flue path
• Maintains a continuous 125mm internal diameter
• Moves the chimney further sideways than a gentler bend
• High-grade stainless-steel inner and outer casings
• Insulation helps maintain the flue-gas temperature
• Fully welded construction provides strength and durability
• Matt-black finish matches other TWPro chimney components
• Push-fit joints support straightforward assembly
• Compatible with matching 125mm TWPro pipes and supports

TWPro 125mm 45 Degree Bend Specification

• Download the TWPro Matt Black information sheet
• View the TWPro installation diagram
• Read why we recommend TWPro twin-wall flue
• Product type: fixed insulated chimney bend
• Nominal internal diameter: 125mm
• Bend angle: 45°
• Construction: two segment
• Inner casing: 0.4mm 316L-grade stainless steel
• Outer casing: 0.4mm 304-grade stainless steel
• Outer finish: high-temperature matt-black coating
• Insulation: 25mm high-density mineral wool
• Construction method: fully welded
• Joint method: push fit with locking bands
• Temperature classification: T600
• 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
• Product code: 37-125-031

Approvals and Classifications

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

The T600 designation classifies the relevant chimney arrangement for flue-gas temperatures up to 600°C. In addition, the G50 designation identifies a soot-fire-resistant arrangement with a declared distance of 50mm from combustible materials.

However, the correct classification depends on the appliance, fuel and complete chimney design. Therefore, follow the appliance instructions and TWPro installation guide.

Suitable Applications

This 125mm TWPro insulated bend may suit correctly specified heating appliances such as:

• Wood-burning stoves
• Multifuel stoves
• Compatible solid-fuel appliances
• Gas coal-effect fires
• Gas boilers
• Oil-fired boilers
• Other compatible gas and oil appliances

However, the appliance outlet size alone does not confirm the correct chimney diameter. First, check the appliance instructions. Next, confirm the required chimney classification. Finally, make sure the complete route complies with Building Regulations and TWPro installation requirements.

Creating an Offset with Two 45 Degree Bends

Installers normally create an offset by using two matching bends. The first bend moves the chimney away from its original line. Then, the second bend returns it to a vertical or parallel route.

The straight pipe between the bends controls the amount of sideways movement. A longer intermediate pipe will normally create a larger offset.

Therefore, check the TWPro offset table or product dimensions before ordering. Also, allow for the joint overlap when calculating the completed height and offset.

Do not calculate the offset from the angle alone. The final measurement depends on the dimensions of both bends, the effective pipe length between them and the depth of each joint.

15, 30 or 45 Degree Bend?

Choose the bend angle according to the amount of sideways movement and the available vertical space:

• 15° bend: suitable for gentle alignment changes and smaller offsets
• 30° bend: provides a moderate offset while keeping the chimney on a strong upward path
• 45° bend: creates the greatest directional change over the shortest distance

A 45° bend can help where the chimney needs to move around a larger obstacle. However, it also creates more resistance than a gentler bend. Therefore, use it only where the designed route requires this angle.

Keep the Chimney Route as Straight as Possible

A straight vertical chimney normally provides the simplest path for combustion gases. Every bend adds resistance and creates another area where soot or combustion deposits may collect.

Therefore, only add a 45° bend where the chimney must avoid an obstacle or make a necessary directional change. Furthermore, keep the total number of bends within the limits stated by the appliance manufacturer, TWPro and Building Regulations.

A complicated route can reduce draught and make chimney sweeping more difficult. Ask a competent installer to check the complete route before ordering.

Two-Segment Construction

This bend uses two formed segments to create the fixed 45° angle. The design provides a controlled directional change while maintaining the 125mm internal flue route.

Fully welded seams provide strength and durability. Meanwhile, the smooth matt-black outer surface creates a professional appearance for visible internal and external installations.

This bend does not provide angle adjustment. Therefore, do not twist, cut or reshape it to achieve a different direction.

How Twin-Wall Insulation Helps

The mineral wool layer sits between the inner flue and outer casing. This insulation helps retain heat as combustion gases pass through the bend.

Warmer flue gases can support chimney draught and help reduce condensation. In addition, the insulation lowers heat transfer to the outer casing when compared with single-wall stove pipe.

However, the bend can still become hot during use. Therefore, maintain the required clearances and prevent accidental contact where necessary.

Strong Stainless-Steel Construction

The inner casing uses corrosion-resistant 316L-grade stainless steel. This surface carries smoke and combustion gases through the chimney.

Meanwhile, the outer casing uses 304-grade stainless steel with a high-temperature matt-black coating. As a result, the bend provides durable protection and matches other TWPro matt-black components.

The stainless-steel construction, mineral wool insulation and fully welded seams create a robust bend for correctly designed chimney installations.

Installation Guidance

First, confirm that the installation requires a 45° change in direction. Next, check the offset dimensions and inspect the bend for damage.

Push each end fully into the adjoining TWPro component. Then secure every connection with the correct locking band. Finally, check that the offset remains aligned, stable and fully supported.

Install each component in the direction shown in the TWPro instructions. Correct joint orientation helps keep condensate and combustion deposits inside the chimney.

Do not cut, reshape or attempt to adjust the bend. Instead, select the correct bend angle and straight pipe lengths for the designed route.

Supporting a 45 Degree Offset

A 45° offset creates sideways forces and places additional weight on the surrounding chimney joints. Therefore, provide suitable structural support above and below the change in direction.

Do not rely on locking bands alone to support the chimney. Instead, use the correct TWPro wall bands, base supports, ceiling supports or roof supports.

The installer must also check the maximum permitted distance between supports and the allowable unsupported height. Follow the current TWPro installation guide for the complete support arrangement.

Distance to Combustible Materials

Maintain at least 50mm between the TWPro insulated chimney and combustible materials for the relevant T600 G50 system arrangement.

Combustible materials can include timber, roof structures, insulation, furniture and other heat-sensitive products. Furthermore, plasterboard may form part of a timber structure and should not automatically count as non-combustible.

Measure the clearance from the closest part of the bend’s outer casing. This check becomes especially important with a 45° offset because the bend can move the chimney closer to nearby building materials.

Keep the required air gap clear. Do not fill it with insulation unless the manufacturer provides a tested component for that exact purpose.

Locking Bands and Joint Security

TWPro uses push-fit joints with locking bands. Push each connection fully together before fitting and closing the band.

The bend creates two connections within the chimney route. Therefore, make sure you have the correct locking band for each joint before starting the installation.

A locking band secures the connection but does not provide structural support. Use separate TWPro support components to carry the chimney weight and control sideways movement.

Can the Bend Pass Through a Wall or Ceiling?

Keep chimney bends and their joints visible and accessible wherever possible. Do not position a bend joint inside a wall, ceiling, floor, roof or other concealed building penetration.

Instead, use straight TWPro pipe with the correct tested sleeve, fire-stop, support or flashing component through the structure.

Plan the offset so both bend joints remain accessible for inspection and sweeping. Always follow the manufacturer’s required joint positions and clearances.

Chimney Sweeping and Cleaning Access

A 45° change in direction can collect more soot and combustion deposits than a straight vertical pipe. Therefore, the complete chimney must provide suitable access for inspection and sweeping.

Consider whether the installation needs an access component near the offset. The chimney sweep must be able to clean the full flue route, including the angled section.

Arrange sweeping at intervals that suit the appliance, fuel and frequency of use. More frequent cleaning may prove necessary when burning fuel that creates higher levels of soot or tar.

Can I Mix TWPro with Another Chimney Brand?

Do not connect this bend to another manufacturer’s twin-wall chimney unless both manufacturers provide written approval.

Different chimney systems can use different outer diameters, joint depths, insulation specifications and locking methods. Therefore, components with the same stated internal diameter may not connect safely.

Using matching TWPro components helps preserve the tested system classification and creates a secure, consistent chimney installation.

Maintenance and Inspection

Inspect the bend, locking bands, welded seams and support components during routine chimney maintenance. Look for movement, corrosion, soot staining or damage to the matt-black finish.

Replace the bend if it becomes badly corroded, distorted, damaged or insecure. Furthermore, arrange a professional inspection if you notice smoke leakage, poor draught or a change in appliance performance.

Why Choose TWPro?

TWPro combines a durable 316L stainless-steel inner casing with a strong 304-grade stainless-steel outer casing. In addition, the mineral wool insulation helps retain heat and supports a stable flue temperature.

The FitSystem push-fit joint makes assembly straightforward, while locking bands secure the connections. Furthermore, the range includes matching pipes, bends, tees, supports, flashings and terminals for a complete chimney installation.

Finally, the smooth matt-black finish creates a professional appearance for modern and traditional properties.

Why Buy from SNH Tradecentre?

• Specialist stove, chimney and flue-system supplier
• Extensive range of matching 125mm TWPro components
• Practical product 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 calculating a 45° offset or selecting the correct support components? Call SNH Tradecentre on 01843 842727 before ordering.

Frequently Asked Questions

What angle is this TWPro bend?

This product has a fixed angle of 45°. Model 37-125-031 identifies the TWPro 125mm two-segment 45-degree bend.

What diameter is the bend?

It has a nominal internal flue diameter of 125mm, which is approximately 5 inches.

Can I use two bends to create an offset?

Yes. Installers commonly use two matching 45° bends with a straight pipe section between them to create an offset.

How do I calculate the offset?

The offset depends on the bend dimensions and the effective installed length of the straight pipe between the two bends. Check the TWPro dimensions before ordering.

Can I adjust the bend angle?

No. This is a fixed two-segment 45° bend. Do not twist, cut or reshape it.

Is a 45-degree bend suitable for every installation?

No. A 45° bend creates more resistance and sideways movement than a gentler bend. Use it only where the appliance instructions, chimney design and relevant regulations permit it.

Can I use it with a wood-burning stove?

Yes, it may suit compatible wood-burning and multifuel appliances. However, check the required diameter and chimney specification in the appliance instructions.

How far must it remain from combustible materials?

The relevant T600 G50 system has a declared distance of 50mm from combustible materials. Measure this clearance from the closest part of the bend’s outer casing.

Can I install the bend inside a wall or ceiling?

Keep bend joints accessible and away from building penetrations. Use straight pipe with the correct tested components where the chimney passes through walls, ceilings, floors or roofs.

Does a 45-degree offset need support?

Yes. The offset creates sideways forces, so use the correct TWPro supports above and below the change in direction.

Can I connect it to another chimney brand?

Do not mix chimney brands unless both manufacturers provide written approval. Similar-looking components may use incompatible joints.

What is the product model?

The product model is 37-125-031.