110mm Soil Pipe Fittings — Socket Plugs, Swept Bends, Branches and Soil Pipe for UK Plumbers

110mm Soil Pipe Fittings — Socket Plugs, Swept Bends, Branches and Soil Pipe for UK Plumbers

110mm soil pipe is the backbone of above-ground drainage in UK domestic and commercial buildings. Every toilet, soil stack, vent pipe, and above-ground foul drain connection uses 110mm soil pipe and fittings. Whether you're replacing a cracked stack, running a new branch for a downstairs WC, or capping off a soil pipe for a pressure test, you need the right fittings to hand. This guide covers the key fittings, when to use each one, and which products APM Electricals stocks at our West London trade counter.

APM Electricals stocks the full Aquaflow 110mm soil pipe range at our trade counter in Acton. 24 Western Avenue, London W3 7TZ. Open Monday to Saturday — call 020 8702 8080 to check stock before you travel.

What Is 110mm Soil Pipe Used For?

In UK above-ground drainage, 110mm (4 inch) is the standard size for:

• Soil stacks — the vertical pipe running from ground floor to roof level that collects WC, bath, and basin waste
• WC branch connections — connecting a toilet outlet directly to the soil stack
• Vent pipes — extending the stack above roof level to ventilate the drainage system and prevent trap siphoning
• Horizontal soil runs — short horizontal lengths connecting a WC to the stack where the WC is offset from the stack position
• Ground floor connections — soil pipe run below suspended floors or through voids connecting to the underground drainage system

110mm soil pipe is regulated under BS EN 1329-1 (PVC-U) and must be installed to comply with Building Regulations Part H (Drainage and Waste Disposal) in England and Wales. Always use fittings from the same system — mixing push-fit and solvent weld fittings requires adapter couplings.

Push-Fit vs Solvent Weld — Which System for Soil Pipe?

110mm soil pipe fittings come in two jointing systems, and the choice matters before you order:

• Push-fit (ring seal) — rubber O-ring seal inside the socket. The spigot pushes in and the ring grips and seals. Joints can be disassembled with a flat-bladed screwdriver if needed. Best for soil stacks where thermal expansion is a factor — the ring seal allows slight axial movement. The most common system for new UK soil stacks.
• Solvent weld — permanent joint made with solvent cement. Stronger and fully sealed, but cannot be taken apart. Used where a rigid permanent joint is needed, typically on horizontal runs or commercial installations. Less common on vertical stacks because it doesn't accommodate thermal expansion.

The Aquaflow range available from APM includes both systems. The socket plug and most stack fittings described in this guide are push-fit.

Black vs Grey — Colour Choice for Soil Pipe

Aquaflow 110mm fittings are available in black and grey. Both are structurally identical — the difference is purely cosmetic:

• Black — more common in new build and modern renovations. Preferred by many plumbers for exposed internal stacks and where the pipework will be visible.
• Grey — the traditional UK soil pipe colour. If you're extending or repairing an existing grey stack, match grey to keep the system consistent. Also available from APM.

Both colours are UV-stabilised for external use if the stack exits through a roof or runs on an external wall.

Key 110mm Soil Pipe Fittings

110mm Pushfit Waste Socket Plug

The socket plug is one of the most frequently used consumable fittings on any drainage job. It pushes into any 110mm ring-seal socket and seals the opening. Common uses include:

• Commissioning and pressure testing — plug all open ends before air-testing the drainage system
• Capping spare branches on soil stacks — new stacks typically include boss adaptors or spare branch sockets; plug unused openings until a future connection is made
• Temporary isolation — seal a soil pipe opening during renovation work to prevent odour ingress or accidental blocking of the drain
• Permanent capping — where a branch connection has been removed or is redundant, a socket plug gives a clean, permanent seal

At £2.03 each, socket plugs are a low-cost fitting that belong in every plumber's van. Stock a handful — you'll reach for one on nearly every soil pipe job.

Aquaflow 110mm Pushfit Waste Socket Plug — Grey — £2.03 inc. VAT

110mm 92.5° Double Socket Swept Bend — Black

The 92.5° swept bend is the standard fitting for connecting a WC outlet to a soil stack or horizontal soil run. The slight sweep (92.5° rather than a dead right angle) maintains flow velocity and reduces the risk of blockage at the bend — critical on a fitting handling solid waste.

Typical applications include:

• WC-to-stack connection — the most common use. The WC outlet connects to one socket, the other socket connects to the horizontal branch running to the stack. The bend sweeps the flow gently toward the stack.
• Horizontal-to-vertical transition — where a horizontal soil run meets the vertical stack, a swept bend makes the direction change without a sharp angle that could cause blockages.
• Offset WC installations — where the toilet is positioned away from the stack and needs a combination of bends to reach the correct connection point.

The double socket version accepts spigots on both ends, making it easy to connect two lengths of pipe or a pipe and a fitting. Available in black and grey.

Aquaflow 110mm 92.5° Double Socket Swept Bend — Black — £8.47 inc. VAT

110mm 135° Double Socket Branch — Black

The 135° branch (also called a 45° branch in some catalogues — same fitting, different naming convention) connects a branch pipe into the main soil stack at a swept angle. Unlike a 90° tee, the 135° branch allows the branch flow to enter the stack in the direction of flow — reducing turbulence, preventing backflow up the branch, and reducing the risk of cross-contamination between adjacent branches.

Key uses:

• Adding a branch to an existing soil stack — where a new WC or soil connection is added to an existing vertical stack, the 135° branch creates a swept connection that meets Part H requirements.
• Multi-appliance stacks — where two or more WCs or soil connections enter the same stack, swept branches ensure each connection enters without disturbing the others.
• New soil stacks — incorporated during initial construction to provide connection points for each floor's WC and soil appliances.

The 135° angle is mandated in most situations by Building Regulations Part H — connections to stacks must be made at an angle to the direction of flow, not perpendicular to it. A 90° tee is only acceptable in specific circumstances (typically single-storey or ground-floor connections).

110mm 135° Double Socket Branch — Black — £9.20 inc. VAT

110mm Plain End Soil Pipe — Black — 1M

Plain end soil pipe is the pipe length itself — the run between fittings. The plain end (spigot) pushes into the socket of each fitting, sealed by the O-ring inside the socket. The 1M length is the most practical size for indoor work — easier to manoeuvre through floors, between joists, and in confined plant room spaces than the 3M length. A 3M length is also available from APM (collection only).

Use cases for the 1M length:

• Short horizontal branches — connecting a WC offset from the stack by 500mm to 1,000mm, a single 1M pipe cut to length is all you need
• Infill sections — when cutting into an existing stack to add a branch, you'll often need a short length of pipe to make up the gap
• Stack construction in confined spaces — stairwells, airing cupboards, and service risers often don't allow full 3M lengths to be handled; 1M sections can be jointed as the stack is built upward
• Trial cuts and fitting offsets — having a 1M length allows you to measure, mark, and cut without wasting a 3M length on a small section

Cut 110mm soil pipe with a fine-tooth hacksaw or plastic pipe cutter. Always chamfer the cut end with a file or deburring tool before pushing into a socket — a sharp edge will damage or displace the O-ring seal.

110mm Plain End Soil Pipe — Black — 1M — £6.68 inc. VAT

Soil Stack Installation — Getting It Right

A few critical rules for 110mm soil stacks that catch out inexperienced plumbers:

Branch Lengths and Connections

• WC branch to stack: maximum 6M horizontal length for a 110mm branch without ventilation
• Connections to the stack must be made using swept branches (135°), not square tees, except on ground-floor single-storey stacks
• Where two branches connect at the same level, offset them vertically by at least 200mm to prevent cross-flow between branches

Stack Fall on Horizontal Runs

• Minimum fall: 1:40 (25mm per metre) for 110mm horizontal soil runs
• Maximum fall: 1:80 — steeper than this and water outpaces solids
• Where horizontal runs connect to the underground drain at ground level, ensure the transition fitting is correctly swept — a sharp-angle bend here is a common blockage point

Stack Ventilation

• The soil stack must be vented to atmosphere — typically by extending the pipe through the roof with a vent cowl
• Air admittance valves (AAVs) can be used where a roof penetration isn't practical, but at least one open vent to atmosphere must exist on the drainage system
• APM stocks 110mm vent cowls in black and grey — ask at the counter

Fire Stopping

• Where a 110mm soil stack passes through a fire-rated floor or wall, the penetration must be fire-stopped with an intumescent collar or sleeve
• Standard PVC-U soil pipe does not provide fire resistance — the fire stopping is provided by the collar around the pipe, not the pipe itself

The Full 110mm Range at APM

APM Electricals stocks the full Aquaflow 110mm soil pipe system, including:

• Socket plugs — pushfit, grey and black
• Plain end soil pipe — 1M and 3M (3M collection only)
• Single and double socket swept bends — 92°, 92.5°, and 135°
• Single, double, and triple socket branches — 92° and 135°
• 90° knuckle bends — single and double socket
• Access bends — with removable access caps for rodding
• Vent cowls — standard and mushroom, black and grey
• Soil-to-rainwater adaptors — 110mm to 68mm round and square
• Plain end couplings and repair couplings

All items available in black; selected items also in grey. Stock levels vary — call 020 8702 8080 or visit the trade counter to confirm availability. Bulk orders for site supply can be arranged.

Where to Buy 110mm Soil Pipe Fittings in London

APM Electricals operates a trade counter at 24 Western Avenue, Acton, London W3 7TZ. We supply plumbers, builders, and electrical contractors across West London and the surrounding area. Our 110mm soil pipe range is available to collect same day — no waiting for delivery on a live job.

Browse the full 110mm soil pipe range at apmi.uk or call 020 8702 8080. We're open Monday to Saturday.