Product Description

TWPro 125mm Twin Wall Insulated 135 Degree Tee Matt Black

Model: 37-125-034

Create a smooth connection at the base of an external chimney with the TWPro 125mm Twin Wall Insulated 135 Degree Tee. The angled branch helps guide the flue gases into the vertical chimney while reducing sharp changes in direction.

The lower branch can also provide access for chimney inspection and sweeping when used with the correct compatible tee cap. As a result, the chimney sweep can reach the base of the flue without taking apart the main chimney sections.

This matt-black insulated tee is often the first main chimney component fitted outside the building. However, it must connect to the correct wall support, tee cap and adjoining TWPro components as part of a complete chimney design.

Key Features

• 125mm internal flue diameter
• 135-degree insulated chimney tee
• Designed for the base of an external chimney
• Provides a smooth change in flue direction
• Helps reduce restriction to the flue gases
• Lower branch can provide cleaning and inspection access
• Requires a compatible tee cap to close the lower branch
• Matt-black powder-coated finish
• 316L-grade stainless-steel inner casing
• 304-grade stainless-steel outer casing
• 25mm high-density mineral-wool insulation
• Push-fit joints with locking bands
• Compatible with TWPro and corresponding KW Flue components
• Suitable for correctly designed T600 chimney systems
• Product model: 37-125-034

TWPro 125mm 135 Degree Tee Specification

Read: Why We Think TWPro Twin-Wall Flue Is the Best

• Download the TWPro Information Sheet
• Download the TWPro Installation Sheet
• Brand: TWPro
• Manufacturer: MI Flues
• Product type: insulated 135-degree chimney tee
• Nominal internal diameter: 125mm
• Approximate external diameter: 175mm
• Finish: matt black
• Inner casing: 0.4mm 316L-grade stainless steel
• Outer casing: 0.4mm 304-grade stainless steel
• Outer coating: heat-resistant matt-black powder coating
• Insulation: 25mm injected mineral wool
• Insulation density: approximately 190kg/m³
• Joint method: push fit with locking bands
• Maximum operating-temperature class: T600
• Declared distance to combustible materials: 50mm
• Manufactured in the United Kingdom
• Product model: 37-125-034

What Is Included?

• 1 x TWPro 125mm Twin Wall Insulated 135 Degree Tee
• Matt-black finish
• Model: 37-125-034

Please note: Check the product images and order details to confirm the supplied locking bands. A compatible tee cap, wall support and other chimney components may need to be ordered separately.

Application

This 135-degree tee normally sits at the base of an external twin-wall chimney. It connects the angled flue route from the building to the vertical chimney above.

Subject to the appliance and chimney-system instructions, suitable applications may include:

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

Always check the appliance manufacturer’s instructions. In particular, confirm the required flue diameter, chimney classification and permitted number of changes in direction.

Why Use a 135 Degree Tee?

A 135-degree tee provides a smoother route into the vertical chimney than a sharp 90-degree connection. Therefore, it can help the flue gases change direction with less resistance.

The angled design also suits external chimney installations where the connecting flue passes through a wall before joining the vertical chimney system.

However, the exact chimney layout must follow the appliance and TWPro installation instructions. The installer must also calculate the correct rise, offset and terminal position.

Cleaning Access at the Base of the Chimney

The lower branch can provide a useful access point for chimney sweeping and inspection. When the installer fits the correct removable tee cap, a chimney sweep can reach the base of the vertical flue.

This position may also collect soot and other debris during sweeping. Therefore, keep the tee cap easy to reach and leave enough space for safe removal.

Do not hide the cleaning point behind permanent boxing, wall finishes or fitted furniture.

Is a Tee Cap Included?

A compatible tee cap may need to be ordered separately. The cap closes the lower branch while allowing future access for cleaning and inspection.

Always use the correct 125mm TWPro or corresponding KW Flue tee cap. Do not use a cap from another chimney system unless the manufacturer confirms compatibility in writing.

External Chimney Installation

This tee is often the first main chimney component installed on the external wall. The angled branch connects to the flue route from the appliance, while the upper connection allows the insulated chimney to continue vertically.

The tee itself should not carry the full weight of the chimney. Therefore, installers normally use the correct load-bearing support components around the base of the vertical system.

Additional wall supports must then secure the chimney at the intervals stated in the TWPro installation instructions.

TWPro System Construction

• 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
• Insulation density: approximately 190kg/m³
• Joint system: push fit with locking bands
• Maximum operating-temperature class: T600

The stainless-steel inner casing provides a durable route for the flue gases. Meanwhile, the mineral-wool insulation helps retain heat within the chimney. The matt-black outer casing then provides protection and a smart finish for visible external installations.

Approvals and System Classification

• Forms part of a 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 every component in the proposed installation before fitting.

Distance to Combustible Materials

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

However, the appliance or another part of the installation may require a greater clearance. Always follow the largest distance stated in the complete installation instructions.

Installation Guidance

• Confirm that a 135-degree tee suits the proposed chimney route
• Check that the appliance requires a 125mm flue
• Plan the position of the wall penetration carefully
• Install the tee in the correct flue-gas direction
• Fit a compatible tee cap to the cleaning branch
• Keep the cleaning point easy to reach
• Fit each adjoining pipe fully into its push-fit connection
• Secure each joint with the required locking band
• Use a suitable load-bearing support at the chimney base
• Fit additional wall supports at the required intervals
• Maintain at least the declared distance from combustible materials
• Follow the appliance and TWPro installation instructions

A suitably competent installer should design and fit the complete chimney. For solid-fuel systems, use a HETAS-registered installer where appropriate.

Supporting the 135 Degree Tee

The tee directs the flue gases and provides cleaning access, but it should not act as the only structural support for the chimney.

Instead, use the correct TWPro base support, wall support or console components for the proposed layout. Proper support prevents the weight of the vertical chimney from placing unwanted pressure on the tee or appliance connection.

Compatibility

This tee fits the 125mm TWPro and corresponding KW Flue systems only. Other chimney manufacturers may use different joint sizes, profiles and locking methods.

Therefore, do not connect this tee to another brand unless the manufacturer confirms compatibility in writing.

The stated 125mm measurement refers to the internal flue diameter. Because the pipe contains 25mm of insulation around the inner casing, its external diameter is approximately 175mm.

Inspection and Maintenance

Check the tee, joints, locking bands and support components during routine chimney maintenance. In addition, inspect the tee cap and make sure it remains secure and correctly fitted.

Arrange regular chimney sweeping based on the appliance, fuel and frequency of use. The lower branch can provide useful access for removing soot and debris from the base of the chimney.

Replace any component that becomes damaged, distorted, heavily corroded or insecure.

TWPro Warranty

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

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

Why Choose the TWPro Twin-Wall System?

TWPro combines a durable 316L stainless-steel inner casing with dense mineral-wool insulation and a matt-black outer casing. In addition, its push-fit joints and locking bands help installers create a secure and tidy chimney route.

The 135-degree tee provides a smooth change in direction while also creating a practical cleaning point at the base of an external chimney.

Why Buy from SNH Tradecentre?

• Specialist supplier of chimney, flue and stove products
• Wide range of matching 125mm TWPro components
• Practical advice from an experienced team
• Close working relationship with MI Flues
• Fast nationwide UK delivery options
• Secure online ordering
• Support before and after your purchase

SNH Tradecentre works closely with MI Flues to process TWPro orders quickly. As a result, we can often arrange same-day dispatch on eligible in-stock orders placed before the relevant cut-off time.

Stock levels, order size and delivery location may affect dispatch times. Therefore, contact us before ordering if you need the component urgently.

Need help planning the base of your external chimney? Call the SNH Tradecentre team on 01843 842727.

Frequently Asked Questions

What is a 135-degree chimney tee used for?

It connects an angled flue route to the base of a vertical chimney. It can also provide cleaning and inspection access through its lower branch.

Where is the tee normally installed?

Installers often fit it as the first main component at the base of an external twin-wall chimney.

Why choose a 135-degree tee instead of a 90-degree tee?

The 135-degree design creates a smoother change in direction. Therefore, it may cause less resistance to the flue gases than a sharper bend.

Does the tee provide sweeping access?

Yes. The lower branch can provide access to the base of the flue when fitted with the correct removable tee cap.

Is the tee cap included?

A tee cap may need to be purchased separately. Check the product contents before ordering.

Does the tee support the chimney?

No. Use the correct TWPro support components to carry the weight of the chimney and secure it to the building.

What diameter is this tee?

It has a nominal internal diameter of 125mm, which is approximately 5 inches. Its external diameter is approximately 175mm.

Can it be used with a wood-burning stove?

Yes, it can form part of a correctly designed 125mm chimney for a compatible wood-burning or multifuel stove.

Does it fit other twin-wall chimney brands?

No. It is designed for compatible TWPro and corresponding KW Flue components. Do not mix chimney brands unless the manufacturer confirms compatibility.

How far must it remain from combustible materials?

The declared clearance is 50mm under the T600 G50 classification. Always follow any greater clearance required elsewhere in the installation.