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Screw-FIX Increaser, 1mm - Ø 175-200mm (25-175-MR1)

Incorporate our high-quality Screw-FIX Increaser into your MI-FLEX flue system for a durable and compliant solution. National Flues delivers top-tier, stainless steel flue components designed to provide a seamless transition between rigid single wall systems and flexible liners. Read more...
Screw-FIX Increaser, 1mm - Ø 175-200mm
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Now only £69.99
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At a Glance

  • 316L stainless steel construction for enhanced durability
  • Transitions flue diameter from 175mm to 200mm for a secure fit
  • Compliant with Building Regulations Document J
  • Suitable for wood (with <20% moisture), oil, gas, and smokeless coal appliances
  • Designed for seamless integration with MI-FLEX liners and easy maintenance

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Have Questions?
Phone: 01670 206999
Email: sales@nationalflues.com

The Screw-FIX Increaser, 1mm thick and sized at Ø 175-200mm, is an essential component for flue system installations. This 316 stainless steel adapter acts as a transitional joint, seamlessly connecting single wall rigid flue systems to the highly flexible MI-FLEX 316 and 904 flue liners. Designed for versatility, it is suitable for solid fuels like wood (moisture content <20%), smokeless coal, gas, and oil, handling temperatures up to 600°C (T600 designation).Building Regulations Document J mandates its installation within masonry chimneys, prohibiting non-masonry enclosures such as timber or plasterboard boxing. The bottom fixings ensure a gas-tight seal using fire cement, ceramic rope, tape, or high-temperature sealant, preventing the flexible liner from being exposed.Easy provision for maintenance is a key feature, requiring routine cleaning and sweeping by a certified professional, preferably a HETAS registered sweep. Solid fuel systems should be swept at least twice annually to ensure safety and efficiency, removing any blockages or deposits like bird nests.

SKU: 25-175-MR1

Delivery Information* +

We work relentlessly to ensure you get your order fast. Estimated delivery for this product is Monday, November 17th. This is based on current lead times. Bear in mind that it is a busy time of year. If you need a product delivered by a specific time in the next 7 days, then please give us a call on 01670 206 999. Visit our Shipping Information page for more information.

About National Flues Ltd +

We began over 30 years ago as a fireplace shop in the North East. We now supply hundreds of trade professionals and thousands of retail customers, all across the UK, every month. We are still a family owned business, lead by the MD Neil, and always try our best to deliver the best possible experience. We also price match, so give us a call if you find this cheaper and want to buy from us. Visit our about us page to read a bit more.

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Technical Specifications
Material316L Stainless Steel
Thickness1mm
Diameter Transition175mm to 200mm
Temperature RatingUp to 600°C (T600)
Fuel CompatibilityWood (<20% moisture), Oil, Gas, Smokeless Coal
StandardsCE / HETAS compliant
System CompatibilitySingle wall flue systems to MI-FLEX 316/904 flue liners
The Screw-FIX Increaser must be installed entirely within a masonry chimney as required by Building Regulations Document J. For optimal performance and safety, secure the increaser using high-temperature materials such as fire cement, ceramic rope, tape, or a high-temperature sealant. It is essential that installation work is carried out by a certified professional, ideally a HETAS registered sweep, to ensure the highest standards of safety and compliance. Regular maintenance is crucial: solid fuel systems should be serviced at least twice a year, while other systems must receive an annual check. Under no circumstances should the flexible flue liner be exposed during the installation process.

The Screw-FIX Increaser is suitable for wood with less than 20% moisture, smokeless coal, gas, and oil appliances, handling temperatures up to 600°C.

The increaser should be installed entirely within a masonry chimney as per Building Regulations Document J. Non-masonry enclosures like timber or plasterboard are not acceptable.

A gas-tight seal can be achieved using fire cement, ceramic rope or tape, or high-temperature sealant. The connection should be made inside the confines of the existing masonry chimney.

Chimneys should be swept and inspected at least once a year by a competent person, with solid fuel systems recommended for sweeping twice a year. Only specialised tools and no chemical cleaners should be used.

No, the flexible flue liner should not be exposed. The transition should occur entirely within the masonry chimney to ensure safety and compliance.

You can find a list of HETAS registered sweeps at www.hetas.co.uk. It's important to use certified professionals for chimney maintenance.

The Screw-FIX Increaser transitions from a 175mm rigid single wall flue to a 200mm flexible flue liner.

 

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