The Ariston Standard Horizontal Flue Kit Ø60/100mm (Part No. 3318073) is the most common flue accessory for Ariston HE condensing boilers — a complete through-wall coaxial horizontal termination assembly for the E-Combi ONE, Clas ONE, Clas System ONE, Genus ONE, Alteas ONE, Alteas ONE+ NET, and E-System ONE ranges. The 1000mm overall length accommodates most standard domestic wall thicknesses in a straightforward straight-through installation, and the push-fit coaxial construction — where combustion gases exhaust through the inner pipe while fresh combustion air enters through the outer annulus — eliminates the need for separate flue and air supply terminations at the wall face. Supplied as a complete set including all components needed for a standard horizontal installation. Also available bundled with the Vertical Starter (3318079) as Part No. 3318074 — useful where the installer wants both flue route options to hand on site.
1000 mm
Overall Kit Length
Push-fit
Connection — No Clamps
HE Range
Boiler Compatibility
⚠ Gas Safe Registered Installer Required: Flue installation must be carried out by a Gas Safe registered engineer in compliance with the Gas Safety (Installation and Use) Regulations 1998, current Building Regulations, and BS 5440-1:2008. Terminal position must comply with the minimum clearances from openings, gutters, and obstructions specified in the boiler installation manual.
⚠ HE Boilers Only — Not Compatible with Next Evo X Water Heaters: The 3318073 belongs to Ariston's HE (High Efficiency) Ø60/100 coaxial flue system and is designed for Ariston condensing boilers only. It is not compatible with the Ariston Next Evo X range of gas water heaters, which use the SE flue system — Part No. 3319648. Do not interchange HE and SE flue accessories.
ℹ Also Available as 3318074 Bundle: If you also need the Vertical Starter (3318079) — for example to give the installer the option to route vertically on the day — the 3318074 supplies this horizontal kit and the vertical starter together in one order. Buy the 3318073 alone when the flue route is confirmed as horizontal and the vertical starter is not needed.
Coaxial Design — Single Wall Penetration
The concentric coaxial construction carries both combustion exhaust gases (inner pipe) and incoming fresh combustion air (outer annulus) through one 100mm hole in the wall. This eliminates the need for a separate air intake grille and reduces the visual impact at the wall face compared to twin-pipe systems.
1000mm Length — Most Walls in One Kit
The 1000mm overall length covers the vast majority of standard UK domestic cavity and solid wall thicknesses without any extensions. The kit can be cut to length on site where the wall is thinner than the kit — follow the installation manual's trimming procedure to ensure the inner pipe seal remains correctly positioned after cutting.
Push-fit Throughout — Fast, Leak-free Assembly
All joints in the HE Ø60/100 system — including the connection to the boiler turret and any extensions or elbows — use push-fit with integral lip seals. No sealant or external clamps are required on flue joints. This speeds installation and eliminates sealant compatibility concerns on condensing flue gas temperatures.
Extendable with HE Accessories
Where walls exceed the kit length or the flue must route around an obstacle, the full HE Ø60/100 accessory range extends and redirects the run: 3318078 (500mm extension), 3318077 (1m extension), 3318465 (2m extension), 3318075 (90° elbow), 3318076 (45° bend pair). Maximum permissible run decreases with each elbow — refer to the installation manual.
Correct Slope — Condensate Drainage
The horizontal flue must be installed with a slight downward fall toward the terminal (approximately 2–3° or 44mm per metre) so that condensate formed in the flue drains away from the boiler rather than back into the heat exchanger. This slope is a Building Regulations and manufacturer requirement — not optional.
Genuine Ariston HE Part
As a genuine Ariston HE flue accessory, the 3318073 is dimensioned and tested to match the HE boiler range's combustion fan pressure, flue gas temperature, and turret geometry. Third-party Ø60/100 kits may vary in internal diameter, gasket sizing, or terminal design in ways that impair combustion performance or compromise weatherproofing — and may void the boiler warranty.
| Specifications — Ariston Standard Horizontal Flue Kit 3318073 |
| Part Number |
3318073 |
| Flue System |
HE Ø60/100 mm coaxial (concentric) |
| Orientation |
Horizontal — through wall |
| Overall Length |
1000 mm |
| Wall Hole Required |
110 mm diameter (core drill) |
| Connection Type |
Push-fit with lip seal — no sealant or clamps on flue joints |
| Compatible Boiler Ranges |
E-Combi ONE 24/30, Clas ONE 24/30/38, Clas System ONE, Genus ONE+ Wi-Fi, Alteas ONE, Alteas ONE+ NET, E-System ONE |
| Not Compatible With |
Ariston Next Evo X gas water heaters — use SE kit 3319648 for those appliances |
| Max Horizontal Run — E-Combi ONE 24 kW |
8 m (Ø60/100) — refer to installation manual for elbow deductions |
| Max Horizontal Run — E-Combi ONE 30 kW |
7 m (Ø60/100) — refer to installation manual for elbow deductions |
| Required Installation Slope |
Fall toward terminal — approx. 2–3° (44mm per metre) |
| Also Available As |
3318074 (this kit + Vertical Starter 3318079, bundled); 3319163 (silver version for Alteas ONE+ NET) |
| HE Extension Accessories |
3318078 (500mm), 3318077 (1m), 3318465 (2m), 3318075 (90° elbow), 3318076 (45° bend pair) |
Frequently Asked Questions
Can I cut the 3318073 kit to fit a thinner wall?
Yes — the kit can be trimmed on site to match the wall thickness. Cut only the outer pipe to the required length; the inner flue pipe must remain at its original length to ensure the exhaust seal is correctly positioned within the boiler turret. Follow the cutting procedure in the Ariston installation manual precisely — incorrect trimming can displace the inner pipe seal and cause flue gas spillage.
What size hole do I need to core-drill through the wall?
A 110mm diameter core-drilled hole is required through the external wall to accommodate the Ø60/100 coaxial flue pipe and allow the wall plate to seat flush. The hole should be drilled with a slight downward slope toward the outside — approximately 2–3° — to ensure correct condensate drainage toward the terminal. Always check the installation manual for the exact offset from the boiler's centreline to the flue outlet position before marking the wall.
What if my wall is thicker than 1000mm, or I need to route around an obstacle?
Add HE Ø60/100 coaxial extension pipes between the boiler turret and the wall terminal: 3318078 (500mm), 3318077 (1000mm), or 3318465 (2000mm). For direction changes, use 3318075 (90° elbow) or 3318076 (45° bend pair). Each elbow reduces the maximum permissible total flue run — check the installation manual's flue length table for the specific deduction per fitting at your boiler's output.
Should I order 3318073 or 3318074?
Order the 3318073 when you are certain the flue will run horizontally and you do not need the Vertical Starter. Order the 3318074 bundle if you also want the Vertical Starter (3318079) available on site — useful when the flue route is not yet confirmed, or for an installer stocking both options. The 3318074 costs marginally more than the 3318073 alone but avoids a second order if the vertical route turns out to be necessary.
Is there a silver version for the Alteas ONE+ NET?
Yes — Part No. 3319163 is the silver-finish version of this horizontal coaxial kit, colour-matched to the Alteas ONE+ NET's premium silver flue range (3319163–3319168). It is mechanically identical to the 3318073; the only difference is colour. Use 3319163 where visible flue pipework should coordinate with the boiler's silver aesthetic.
