Product Description

125mm to 150mm Vitreous Enamel Flue Increaser – 67-125-002

The 125mm to 150mm Vitreous Enamel Flue Increaser connects compatible 125mm VIT-Smooth pipe below to compatible 150mm flue pipe above.

This adaptor increases the flue diameter by 25mm, changing from 125mm or 5 inches to 150mm or 6 inches. Therefore, it can create a neat transition where the appliance and chimney design require the flue to increase in size.

VIT-Smooth makes the increaser from strong 1.2mm zero-carbon steel. In addition, its internal and external vitreous enamel coating provides a durable matt-black finish that complements many traditional and modern stoves.

Product Guide and Further Information

• Download the VIT-Smooth brochure

VIT-Smooth 125mm to 150mm Increaser Features

• Vitreous enamel flue increaser
• Manufacturer part number: 67-125-002
• Increases from 125mm to 150mm
• Connects 5-inch pipe below to 6-inch pipe above
• Increases the flue diameter by 25mm
• Designed for compatible VIT-Smooth components
• Manufactured from 1.2mm zero-carbon steel
• Approximately 0.2mm vitreous enamel coating
• Approximate total thickness: 1.4mm to 1.5mm
• Internal and external enamel coating
• Smooth matt-black finish
• Friction-fit joint system
• Suitable for compatible wood-burning appliances
• Suitable for compatible multi-fuel appliances
• Suitable for compatible gas and oil appliances
• Maximum continuous temperature class: 600°C
• Minimum clearance from combustible materials: 375mm
• Manufactured to EN 1856-2
• Designed for visible single-wall connecting flue systems
• 12-year warranty, subject to the manufacturer’s terms

Technical Specification

• Brand: VIT-Smooth
• Manufacturer: MI-Flues
• Part number: 67-125-002
• Product type: Single-wall flue increaser
• Lower nominal diameter: 125mm / 5 inches
• Upper nominal diameter: 150mm / 6 inches
• Increase in diameter: 25mm / 1 inch
• Material: Zero-carbon steel
• Steel thickness: 1.2mm
• Enamel thickness: Approximately 0.2mm
• Total coated thickness: Approximately 1.4mm to 1.5mm
• Finish: Matt-black vitreous enamel
• Joint type: Friction fit
• Temperature classification: T600
• Pressure class: N1
• Soot-fire resistance: G
• Minimum distance from combustibles: 375mm
• Product standard: EN 1856-2
• Full classification: T600 N1 Vm L80120 G375
• Approximate weight: 0.8kg
• GTIN / EAN: 5060795860321

What Does a Flue Increaser Do?

A flue increaser changes the system from a smaller diameter below to a larger diameter above. This model changes from 125mm to 150mm.

For example, an installer may use it above a compatible 125mm stove pipe when the chimney liner, chimney connection or approved flue system above requires a 150mm connection.

However, this fitting does not connect directly to every type of flexible liner or twin-wall chimney. A suitable system adaptor may also be required.

Correct Installation Direction

The 125mm smaller end must face downwards towards the appliance. Meanwhile, the 150mm larger end faces upwards towards the chimney or flue system.

This arrangement allows the flue diameter to increase in the direction of the rising combustion gases. It also helps keep soot and condensate inside the flue system.

Do not install the increaser upside down as a reducer. The appliance and flue manufacturers must approve any change in chimney diameter.

Increaser or Reducer?

This product is an increaser. It changes from 125mm below to 150mm above when installed in the correct direction.

It must not be used to reduce a 150mm appliance outlet to a 125mm chimney. Reducing a flue below the appliance manufacturer’s stated outlet size can restrict combustion gases and create a serious safety risk.

If you are unsure which direction the flue needs to change, ask a competent installer before ordering.

Suitable Applications

• Increasing compatible 125mm pipe to 150mm
• Connecting a 5-inch stove pipe to a 6-inch system
• Compatible wood-burning stove installations
• Compatible multi-fuel stove installations
• Suitable solid-fuel appliances
• Suitable gas appliances
• Suitable oil-fired appliances
• Visible single-wall connecting flue systems

The appliance manufacturer must allow the proposed flue arrangement. Furthermore, the chimney must provide the correct diameter, height, draught and temperature rating for the appliance.

Connecting to Flexible Flue Liner

This increaser changes the diameter between compatible VIT-Smooth components. It is not a flexible liner connector.

If the 150mm connection needs to join a flexible chimney liner, the installation may also require a suitable 150mm rigid-to-flex adaptor. The flexible liner must remain inside a suitable existing masonry chimney.

Therefore, confirm every part of the connection before ordering. The installer should check the increaser, rigid pipe, liner adaptor and flexible liner as one complete system.

Connecting to Twin-Wall Flue

Do not connect this single-wall increaser directly to twin-wall pipe unless the twin-wall manufacturer provides a compatible and approved adaptor.

Different flue systems use different joint designs and outside diameters. Therefore, two components described as 150mm may not connect directly.

Why Choose VIT-Smooth?

VIT-Smooth uses carefully finished welds and a smooth enamel surface to create a clean appearance. Its deep matt-black colour also complements many UK stoves and fireplace settings.

Furthermore, the 1.2mm steel construction creates a strong base beneath the vitreous enamel. The complete coated thickness measures approximately 1.4mm to 1.5mm.

The enamel covers both the internal and external surfaces. As a result, it helps protect the steel against high temperatures, combustion gases and normal corrosion.

Important Installation Restrictions

Do not use this single-wall increaser or connecting pipe to pass through a wall, ceiling, roof, loft or concealed void. Instead, change to a suitable insulated chimney system before reaching these areas.

The product has a G375 classification. Therefore, it requires a minimum clearance of 375mm from combustible materials such as timber and some wall or ceiling finishes.

However, the appliance instructions may require a greater clearance. If so, the installer must always follow the greater distance.

Does the Joint Need Sealing?

The VIT-Smooth system uses friction-fit joints. However, fitting requirements may vary according to the component, appliance and complete installation.

For extra security, suitable fire cement or high-temperature sealant may be used where the manufacturer permits it. Therefore, follow the latest VIT-Smooth instructions for every connection.

Do not rely on sealant to make incompatible components fit. Every joint must have the correct mechanical engagement before sealing.

Can the Increaser Be Cut?

Although some VIT-Smooth pipe sections can be shortened, cutting an increaser may alter its socket, spigot or transition profile. Therefore, avoid cutting this component unless the manufacturer expressly permits it.

If an installer exposes bare steel during any approved alteration, they must protect it with suitable high-temperature paint to reduce the risk of corrosion.

Inspection and Cleaning

The complete chimney system must allow safe inspection and cleaning. Therefore, the installation may require an access-door component near the appliance or at a change in direction.

Solid-fuel chimneys need regular sweeping to remove soot and deposits. The correct frequency depends on the appliance, fuel and level of use. Always follow the appliance instructions and use a competent chimney sweep.

Why Buy from SNH Tradecentre?

• Competitive prices: We aim to offer excellent value across our stove and flue range.
• Collection available: Collect from our Birchington trade counter when the increaser is in stock.
• Delivery options: We offer convenient delivery throughout eligible UK areas.
• Helpful advice: Our team can help you compare common flue diameters and adaptors.
• Clear product information: We provide useful fitting and compatibility details.
• Genuine products: Buy from an established plumbing and heating merchant.
• Trade and public welcome: We supply installers, businesses, landlords and homeowners.
• Independent merchant: SNH Tradecentre is based in Birchington, Kent.

Need Help Choosing a Flue Increaser?

Not sure whether this adaptor suits your installation? Call SNH Tradecentre on 01843 842727. Please have the appliance make, model, outlet diameter and proposed chimney size available.

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Installation Requirements

A competent installer should design and fit the complete flue system. For solid-fuel appliances, use a HETAS-registered installer or notify Local Authority Building Control where required.

The installer must follow the appliance instructions, flue manufacturer’s guidance and current Building Regulations. They must also check the flue diameter, chimney route, ventilation, clearances, supports and sweeping access.

A carbon monoxide alarm must be installed where current regulations require one. However, an alarm does not replace correct installation, regular maintenance or chimney sweeping.

Frequently Asked Questions

What sizes does this increaser connect?

It connects compatible 125mm pipe below to compatible 150mm pipe above. These sizes are also commonly described as 5 inches and 6 inches.

Which end faces downwards?

The smaller 125mm end must face downwards towards the appliance. The larger 150mm end faces upwards towards the chimney.

Can I use it as a 150mm-to-125mm reducer?

No. This fitting is designed as an increaser. Do not use it to reduce a 150mm appliance outlet to a 125mm flue.

Will it connect directly to flexible liner?

Not normally. A suitable rigid-to-flex liner adaptor may also be required. Confirm the complete connection with the installer before ordering.

Will it connect directly to twin-wall flue?

Only through a compatible adaptor approved by the twin-wall manufacturer. Do not force components from different systems together.

What is the maximum temperature rating?

The increaser has a T600 classification. Therefore, its maximum continuous operating temperature class is 600°C.

How far must it be from combustible materials?

The G375 classification requires a minimum clearance of 375mm. However, use any greater clearance required by the appliance or installation instructions.

Can it pass through a wall or ceiling?

No. This is a single-wall connecting component. It must not pass through walls, ceilings, roofs, lofts or concealed areas.

Does the joint require fire cement?

The system uses friction-fit joints. However, suitable fire cement or high-temperature sealant may be used where current manufacturer instructions permit it.

Who should install the increaser?

A competent installer should fit it as part of a correctly designed flue system. For solid-fuel work, a HETAS-registered installer can complete and certify the installation where the scheme applies.

Order the 125mm to 150mm VIT-Smooth Increaser

Choose the 125mm to 150mm VIT-Smooth Vitreous Enamel Flue Increaser 67-125-002 to create a neat transition from compatible 5-inch pipe below to 6-inch pipe above.

Before ordering, confirm the appliance requirements, direction of increase and compatibility with every other part of the proposed flue system.

Manufacturers may update specifications and installation guidance. Therefore, check the latest VIT-Smooth instructions and confirm suitability with a competent installer before ordering.