What’s the impact of reducing duct size?

Stepping down increases air velocity and static pressure. That can lower overall airflow on long/complex runs and may make fans work harder. Keep the transition as short and smooth as possible and check your fan’s performance curve if airflow is critical.

How should I install the reducer correctly to ensure a tight fit?

Push-fit the reducer fully into the matching female duct/fitting until it seats. Seal joints with foil tape or duct mastic, and support adjacent ducting with clips/hangers to prevent movement.

Will using this reducer affect airflow and noise levels?

Possibly. Higher air velocity through the 100 mm section can add turbulence and noise, especially near bends. Minimising kinks, keeping runs short/straight, and using smooth-bore rigid ducting helps keep noise down.

Can I use this reducer in high-pressure systems or extractor fans?

Yes for typical domestic/commercial extractor fans and MVHR/ventilation systems. For high static pressure industrial setups, confirm suitability against your system specs; some applications may require metal components or purpose-rated fittings.

Do I need to insulate the reducer when installing it in cold spaces?

If warm, moist air passes through unheated areas, add insulation (or use insulated duct nearby) to reduce condensation risk and heat loss.

What materials is the reducer made of, and are they fire-resistant?

It’s a rigid, flame-retardant plastic reducer suitable for standard ventilation temperatures. It’s not designed for very high-temperature extraction.

What do “male” and “female” ends mean on the reducer?

“Male” ends push into duct or fittings. “Female” ends accept a male spigot. This reducer’s ends act as male spigots for 150 mm and 100 mm round plastic duct/fittings.

Can I connect straight to fan spigots, or do I need additional ducting?

If the fan spigot is female, the reducer can push straight in. If the fan spigot is male, sleeve the joint with a short piece of matching round duct or use a straight female connector for a neat, airtight fit.

150mm To 100mm Rigid Plastic Reducer

Q: What materials is the reducer made of, and are they fire-resistant?

It&rsquo;s a rigid, flame-retardant plastic reducer suitable for standard ventilation temperatures. It&rsquo;s not designed for very high-temperature extraction.

Q: What do “male” and “female” ends mean on the reducer?

&ldquo;Male&rdquo; ends push into duct or fittings. &ldquo;Female&rdquo; ends accept a male spigot. This reducer&rsquo;s ends act as male spigots for 150 mm and 100 mm round plastic duct/fittings.

£3.02 £3.62 inc VAT

In stock and ready for dispatch

Product Description

A circular reducer is a simple, reliable way to connect round pipe ducting, flexi-hose and fan spigots. This 150 mm → 100 mm rigid plastic reducer gives you a smooth transition for long duct runs where space is tight, helping to minimise turbulence and maintain strong airflow. Ideal for bathrooms, toilets, utility rooms and compact plant spaces, and widely used in whole-house ventilation, passive stack, PIV, AC/HVAC and MVHR systems.

Key benefits

Low resistance transition – smooth, round profile helps maintain airflow.
Quick push-fit – the 150 mm end is male to push into standard 150 mm round duct (female).
Space-saving – steps down cleanly where a smaller run is required.
Tough & lightweight – rigid, flame-retardant plastic for DIY and trade.
Versatile – use between duct runs, flexi-hose and fan spigots (see fitment notes).

Fitment & compatibility

150 mm side: male spigot; push-fits into 150 mm round plastic duct/compatible female fittings.
100 mm side: use as a male spigot into 100 mm round duct.
Connecting to male fan spigots or other male fittings: sleeve with a short piece of matching round duct or use a straight female connector for a neat, airtight join.
Works with round rigid plastic ducting; to join flexible hose, use the appropriate hose cuff and jubilee clip.

Specifications

Property	Detail
Size / transition	150 mm (Ø) to 100 mm (Ø)
Shape	Round, in-line reducer
Material	Rigid, flame-retardant plastic
Finish	Smooth internal bore
Typical use	Ventilation/air extraction, bathrooms, toilets, utilities, HVAC/MVHR
Compatibility	Standard UK round plastic duct and fittings (150 mm / 100 mm)

Note: Suitable for typical domestic/commercial ventilation temperatures. Not intended for very high-temperature extraction.

Installation tips

Plan the run to keep it as short and straight as possible.
Push-fit fully so the reducer seats against the duct stop.
Sleeve where needed: if meeting a male spigot, insert a short length of duct or a female straight connector.
Seal joints with duct tape or mastic for an airtight finish; support longer runs with clips/hangers.

What’s in the box: 1 × 150 mm → 100 mm rigid plastic reducer.

Helpful accessories

150 mm & 100 mm round duct lengths
150 mm and 100 mm straight female connectors
150 mm/100 mm bends & tees
Duct clips/hangers, foil tape, duct sealant
100 mm/150 mm hose cuffs + jubilee clips (for flexible hose)

Please call if you require any assistance or help choosing the correct products. Our aim is to ensure that your purchase goes smoothly and is delivered on time.

Please note: we may send out like for like products from different manufacturers.

You can call us on 01455 819 729 or email [email protected]

Visit our trade counter: Unit 3 Claymill Road, Leicester, LE4 9JJ. We are open from Monday to Thursday 8am till 5pm and Friday 8am till 3pm.

Customers rate our excellent service at 4.8 out of 5, based on 829 reviews.

Please call if you require any assistance or help choosing the correct products. Our aim is to ensure that your purchase goes smoothly and is delivered on time.

Please note: we may send out like for like products from different manufacturers.

You can call us on 01455 616 444 or email [email protected]

Visit our trade counter: Unit 3 Claymill Road, Leicester, LE4 9JJ. We are open from Monday to Thursday 8am till 5pm and Friday 8am till 3pm.

Customers rate our excellent service at 4.8 out of 5, based on 833 reviews.

Downloads

150mm To 100mm Reducer Data Sheet 513KB

FAQ

What’s the impact of reducing duct size?: Stepping down increases air velocity and static pressure. That can lower overall airflow on long/complex runs and may make fans work harder. Keep the transition as short and smooth as possible and check your fan’s performance curve if airflow is critical.
How should I install the reducer correctly to ensure a tight fit?: Push-fit the reducer fully into the matching female duct/fitting until it seats. Seal joints with foil tape or duct mastic, and support adjacent ducting with clips/hangers to prevent movement.
Will using this reducer affect airflow and noise levels?: Possibly. Higher air velocity through the 100 mm section can add turbulence and noise, especially near bends. Minimising kinks, keeping runs short/straight, and using smooth-bore rigid ducting helps keep noise down.
Can I use this reducer in high-pressure systems or extractor fans?: Yes for typical domestic/commercial extractor fans and MVHR/ventilation systems. For high static pressure industrial setups, confirm suitability against your system specs; some applications may require metal components or purpose-rated fittings.
Do I need to insulate the reducer when installing it in cold spaces?: If warm, moist air passes through unheated areas, add insulation (or use insulated duct nearby) to reduce condensation risk and heat loss.
What materials is the reducer made of, and are they fire-resistant?: It’s a rigid, flame-retardant plastic reducer suitable for standard ventilation temperatures. It’s not designed for very high-temperature extraction.
What do “male” and “female” ends mean on the reducer?: “Male” ends push into duct or fittings. “Female” ends accept a male spigot. This reducer’s ends act as male spigots for 150 mm and 100 mm round plastic duct/fittings.
Can I connect straight to fan spigots, or do I need additional ducting?: If the fan spigot is female, the reducer can push straight in. If the fan spigot is male, sleeve the joint with a short piece of matching round duct or use a straight female connector for a neat, airtight fit.

Ducting Express Services Ltd

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Based on 833 customer reviews