150mm Round PVC Ducting Pipe

150mm round PVC ducting pipe — also called 6 inch ducting, 150mm plastic pipe, 150mm plastic ducting, or Domus EasiPipe System 150 — is rigid round ductwork for 150mm MVHR trunks, large cooker hoods, commercial in-line extract fans, whole-house ventilation systems and any duty over roughly 250 m³/h. It's the largest size in the domestic Domus round range and the default specification for MVHR main supply and extract runs between the unit and the first branch. 150mm carries roughly 2.25x the airflow of 100mm at the same velocity with the lowest pressure loss of the domestic range.

We stock the full Domus EasiPipe range in 150mm: 2m, 1m and 350mm straight lengths, 90° bends, T-pieces, Y-pieces, straight connectors, spigot adaptors (100mm to 150mm, 125mm to 150mm, 150mm to 200mm), hose connectors, pipe clips, the Domus high-rise cowl installation kit for apartments and tall buildings, flexible EasiPipe hose in 3m and 6m coils, plus 150mm x 10m insulated aluminium flex for MVHR. All rigid parts are push-fit with gasketed sockets. 

All Round PVC Ducting / 100mm Round / 125mm Round / 220x90 Flat Equivalent / 150mm Flexible

What is 150mm round ducting?

150mm round ducting is rigid circular PVC ductwork with a 150mm internal diameter — the UK standard largest-domestic size. It's sometimes called 6 inch ducting (150mm is the metric equivalent of the imperial 6 inch size), and in the Domus system it's branded EasiPipe System 150. The 150mm diameter carries approximately 2.25x the airflow of 100mm at the same velocity with the lowest pressure loss of any domestic size, so it's specified for duties where smaller sizes would be marginal — MVHR trunks, large cooker hoods, commercial in-line extract, and extract duties above 250 m³/h.

What is 150mm round ducting used for?

MVHR main supply and extract trunks (between the unit and the first branch in whole-house ventilation systems), large domestic cooker hoods with a 150mm spigot (most professional-grade or island hoods over 900mm wide), high-flow in-line centrifugal fans (S&P TD-Silent-ECOWATT 250, Vent-Axia ACM150, similar), twin-fan light-commercial extract on offices and treatment rooms, and any domestic extract duty where 125mm would run at too high a velocity or pressure drop. For branch runs from the MVHR trunk to room terminals, step down to 125mm or 100mm using Domus spigot adaptors.

Is 150mm round the same as 6 inch ducting?

Yes — 150mm is metric, 6 inch is imperial, same nominal duct size. UK ducting is manufactured in metric (150mm internal diameter) but older specifications and some hood manufacturers still use the 6 inch label. Any 6 inch branded cooker hood, in-line fan or wall kit will connect to standard 150mm round EasiPipe ducting.

What's in the Domus EasiPipe 150mm range?

The full EasiPipe System 150 round range: 2m straight lengths (1200-6), 1m straights (1100-6 and 2100-6), 350mm short straight (135-6) for tight sections, 90° right-angle bends (690), T-pieces (692) for branched runs, Y-pieces (699M) for split runs, straight connectors (693), pipe fasteners and clips (696), flexible hose connector (680, 150mm x 70mm), spigot adaptors stepping up from 100mm (619), 125mm (118) and up to 200mm (819), and the Domus 2647B high-rise cowl installation kit for apartment and tall-building terminations. Flexible 150mm EasiPipe hose in 3m (663) and 6m (666) coils for short awkward runs, plus 150mm x 10m insulated aluminium flex (6210) for MVHR branches where thermal performance matters.

Should I use 150mm round or 220x90 flat ducting?

Airflow-equivalent, the choice depends on void depth and specification. Use 150mm round wherever depth allows (150mm+) — it has the lowest pressure loss of the range, connects directly to any 150mm fan or hood spigot, and is the correct choice for MVHR trunks where pressure loss directly affects fan power. Use 220x90 flat where depth is restricted — above kitchen wall units for a 150mm hood, through shallow ceiling voids, or concealed in stud work. For MVHR specifically, most installers route rigid 150mm round for the unit-to-first-branch trunk run and only switch to flat or flexible at branch points where space demands it.

Should I use 150mm round or 150mm flexible ducting?

Rigid EasiPipe for anything that matters — MVHR, Building Regs extract, large cooker hoods, commercial installations. Flexible 150mm hose has significantly higher pressure loss (2–3x per metre), sags without constant support, and traps grease and dust in its corrugations. Use flexible only for short final connections (fan spigot to rigid duct, hood to rigid duct) or for awkward access where rigid is physically impossible. For MVHR specifically, insulated aluminium flex (Domus 6210) is sometimes specified for short branch runs but the main trunk must be rigid.

Is 150mm round ducting suitable for MVHR?

Yes — 150mm round rigid is the default specification for MVHR main trunks on most domestic units (Vent-Axia Sentinel, Zehnder ComfoAir, Systemair SAVE, etc). The MVHR unit itself has a 150mm or 180mm spigot, and the trunk runs in 150mm until it reaches the manifold or first branch. The full EasiPipe 150 system supports this: 2m straights to minimise joints, 90° bends, Y-pieces for splitting trunks, and the 150-to-125mm step-down (118) for branch reductions. Pair with the Domus insulated flex (6210) for any trunk section passing through an unheated loft or cold roof void.

How do I join 150mm EasiPipe sections?

EasiPipe uses push-fit joints with integral neoprene gaskets. Slide the plain end of one duct into the socketed end of the next, or use a straight connector (Domus 693) to join two plain ends. For airtight joints — essential on MVHR and Building Regs extract — apply duct sealant inside the socket before pushing home, then foil-tape over the joint externally. Fix horizontal runs every 600–800mm with pipe clips (Domus 696) to prevent sag; large-diameter duct is heavier than 100mm so support is more critical. Bends, T-pieces and Y-pieces have sockets at each leg.

Do I need to insulate 150mm ducting?

Yes, for any run through a cold space — unheated loft, cold roof, external, or uninsulated outbuilding. Warm moist extract or supply air hitting a cold duct wall causes condensation inside the duct that pools, drips back to the fan, or in MVHR systems can drain into the heat exchanger and cause failures. On MVHR supply runs through cold spaces, insulation also prevents the heated air losing temperature before reaching the rooms. Wrap rigid 150mm in site-applied duct insulation, or use the Domus 150mm x 10m insulated aluminium flex (6210) for branch runs where rigid can't easily be insulated to the required standard.

Can I terminate 150mm ducting through the roof on a tall building?

Yes — the Domus 150mm high-rise cowl installation kit (2647B) is designed for apartment blocks, flats and tall-building terminations where a standard wall grille isn't practical. The kit includes the cowl and the fittings to connect the 150mm EasiPipe run to the roof terminal. For single-dwelling installations, terminate with a standard 150mm external cowl or grille with integral backdraught shutter. Never leave a duct end open; insulate any external or cold-loft run to prevent condensation.