Product Description

TWPro 125mm Twin Wall Insulated Rain Cap – Matt Black

Model: 37-125-090

Finish your insulated chimney with the TWPro 125mm Twin Wall Insulated Rain Cap. This matt-black chimney terminal helps reduce direct rain entry while still allowing combustion gases to leave the flue.

The rain cap connects directly to a compatible 125mm TWPro twin-wall chimney section. In addition, the durable matt-black finish matches other components in the TWPro black flue range.

Please note: a rain cap helps minimise water entry, but it cannot stop every drop of wind-driven rain. Therefore, the complete chimney should still include a suitable way to manage rainwater and condensate.

Product at a Glance

• 125mm nominal internal flue diameter
• Standard rain-protection chimney terminal
• Helps minimise direct rain entry
• Allows combustion gases to leave the chimney safely
• Matt-black external finish
• 316L stainless-steel inner casing
• 304-grade stainless-steel outer casing
• High-density mineral wool insulation
• Push-fit joint with locking band
• 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: 37-125-090

What Does a Twin-Wall Rain Cap Do?

A rain cap fits at the top of a chimney and places a protective cover above the flue outlet. As a result, it helps reduce the amount of rain that can fall directly into the chimney.

At the same time, the open sides allow smoke and combustion gases to escape. Therefore, the cap protects the flue without closing or restricting the outlet.

This model forms part of the TWPro 125mm twin-wall insulated chimney system. Consequently, it provides a secure and visually consistent terminal for compatible matt-black TWPro installations.

Key Features

• Protective top helps shield the flue from direct rainfall
• Open sides allow smoke and combustion gases to escape
• Suitable for compatible 125mm TWPro chimney systems
• Strong stainless-steel construction
• High-temperature matt-black coating
• Fully welded parts provide strength and durability
• Insulated design helps maintain the flue temperature
• Supplied with a locking band for a secure connection
• Suitable for internal or external chimney routes when correctly specified
• Matches the appearance of other TWPro matt-black components

Rain Protection for Your Chimney

Rainwater can enter an uncovered chimney and run down the internal flue. Over time, this moisture may mix with soot and combustion deposits. Therefore, fitting the correct terminal forms an important part of a complete chimney design.

The TWPro rain cap places a cover above the outlet to reduce direct rainfall. However, strong winds can still carry some rain beneath the cap. For this reason, the chimney should include suitable condensate and rainwater management where the system design requires it.

This cap does not seal the chimney against moisture. Instead, it provides practical rain protection while keeping the flue outlet open.

Is This an Anti-Downdraught Cowl?

No. This product is a standard rain cap rather than a specialist anti-downdraught cowl.

Its main purpose is to reduce rain entry. It does not guarantee protection against downdraught caused by nearby buildings, trees, roof shapes or exposed locations.

Therefore, ask a competent installer to assess the site if the property has an existing smoke, wind or downdraught problem. A different approved terminal or changes to the chimney height may prove more suitable.

TWPro 125mm Rain Cap Specification

• Download the TWPro Matt Black information sheet
• View the TWPro installation diagram
• Read why we recommend TWPro twin-wall flue
• Product type: insulated twin-wall rain cap
• Nominal internal diameter: 125mm
• 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: fully welded
• Joint method: push fit with locking band
• 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: 37-125-090

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 system with a declared 50mm distance to combustible materials.

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

Suitable Applications

This 125mm rain cap may suit correctly specified solid-fuel, oil and gas appliances. Examples can include:

• Wood-burning stoves
• Multifuel stoves
• Compatible solid-fuel appliances
• Gas coal-effect fires
• Gas boilers
• Oil-fired boilers

First, confirm that the appliance requires a 125mm internal flue diameter. Next, check that the TWPro system carries the correct classification for the appliance and fuel. Finally, make sure this style of terminal suits the installation location.

Do not choose the flue diameter from the appliance outlet alone. The appliance instructions, chimney design and relevant regulations determine the required diameter.

Strong Stainless-Steel Construction

The inner casing uses corrosion-resistant 316L-grade stainless steel. Meanwhile, the outer casing uses strong 304-grade stainless steel with a high-temperature matt-black coating.

Between the two casings, high-density mineral wool insulation helps the flue gases retain heat. Consequently, the insulated construction supports a stable chimney temperature and reduces external surface temperatures.

The fully welded construction also improves strength. As a result, the rain cap can withstand the demands of an exposed chimney position when installers fit and support it correctly.

Why Choose a Matt-Black Terminal?

The matt-black surface creates a smart and modern appearance. It also allows the terminal to match visible black chimney sections, roof supports and wall bands.

This finish works particularly well with black stoves and external chimney systems. However, the coating still needs regular inspection because weather, installation damage and chimney deposits can affect its appearance over time.

Installation Guidance

Fit the rain cap to the top of the final vertical TWPro chimney section. First, check that the joint is clean and free from damage. Next, push the terminal fully into position. Finally, secure the connection with the supplied locking band.

The cap must remain upright, secure and properly supported. However, do not use the terminal to support the chimney sections below it. Instead, use the correct TWPro wall supports, roof supports and structural components throughout the installation.

The chimney outlet must also finish at the correct height and position. Nearby roofs, windows, doors, trees and buildings can affect flue performance. Therefore, always follow the TWPro instructions, appliance requirements and Building Regulations.

Does the Locking Band Come with the Rain Cap?

Yes. The manufacturer lists a locking band with this rain cap. The band secures the push-fit joint between the terminal and the final TWPro chimney section.

Make sure the joint engages fully before closing the locking band. In addition, inspect the band after installation to confirm that it remains tight and correctly positioned.

Distance to Combustible Materials

Maintain a minimum distance of 50mm between the TWPro insulated chimney and combustible materials for the relevant T600 G50 system arrangement.

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

Do not fill the required air gap with insulation unless the manufacturer provides a tested component for that exact purpose. Also, follow any greater clearance stated by the appliance manufacturer or another part of the chimney design.

Rainwater and Condensate Management

Although the cap reduces direct rain entry, some water may still enter during severe or wind-driven weather. Condensation can also form inside a chimney under certain operating conditions.

Therefore, the complete system should provide a suitable way to collect and discharge moisture where required. For example, an external chimney may use a tee with a compatible tee cap and condensate drain at its base.

Regularly check that any drain remains clear. Otherwise, water could collect inside the chimney or travel towards the appliance.

Maintenance and Cleaning

Inspect the rain cap regularly for soot, debris, bird nesting material and weather damage. In addition, check that the locking band remains secure.

Arrange chimney sweeping at intervals that suit the appliance, fuel and frequency of use. During sweeping, ask the chimney sweep to inspect the terminal, internal flue and supporting components.

Replace the cap if it becomes badly corroded, distorted or insecure. You should also arrange an inspection if you notice smoke leakage, poor chimney performance or unusual water entry.

Can I Mix TWPro with Another Chimney Brand?

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

Different chimney brands can use different dimensions, joint depths, insulation types and locking methods. Therefore, parts with the same stated internal diameter may not connect safely.

Using matching TWPro components helps preserve the tested system classification and provides a secure installation.

Why Choose the TWPro Chimney System?

TWPro combines a durable stainless-steel inner casing with an insulated outer construction. As a result, the system provides a strong and practical chimney solution for many domestic heating appliances.

The push-fit joint design also makes assembly straightforward. Once the sections engage, the locking band secures the joint. Furthermore, the wide range of matching pipes, bends, tees, supports, flashings and terminals helps installers create a complete chimney route.

Finally, the smooth matt-black surface produces a professional finish for both modern and traditional properties.

Why Buy from SNH Tradecentre?

• Specialist stove, chimney and flue-system supplier
• Extensive range of matching TWPro components
• 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 checking the terminal, flue diameter or matching components? Call SNH Tradecentre on 01843 842727 before ordering.

Frequently Asked Questions

What size chimney does this rain cap fit?

It fits a compatible TWPro chimney with a nominal internal diameter of 125mm, which is approximately 5 inches.

Will this cap completely stop rain entering the chimney?

No rain cap can guarantee complete protection from wind-driven rain. However, this cap helps minimise water entering directly through the flue outlet.

Is this an anti-downdraught cowl?

No. It provides standard rain protection but does not specifically solve downdraught problems.

Can I use it with a wood-burning stove?

Yes, it can suit compatible wood-burning and multifuel stoves. However, you must confirm the required flue diameter and chimney specification in the appliance instructions.

Can I use it with a gas or oil appliance?

Yes, the TWPro system carries classifications for compatible gas and oil applications. A competent installer must confirm the correct classification and terminal type.

Does the rain cap include a locking band?

Yes. The rain cap comes with a locking band to secure it to the compatible TWPro chimney section.

How far must the chimney remain from combustible materials?

The relevant T600 G50 system has a declared distance of 50mm from combustible materials. However, another part of the installation may require a greater clearance.

Does this rain cap have insulation?

Yes. High-density mineral wool sits between the stainless-steel inner and outer casings.

Can I fit it to another brand of twin-wall chimney?

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

What is the product model?

The product model is 37-125-090.