Pegasus Pressfit Copper Pipe Fittings — 15mm, 22mm and 28mm M-Profile Couplers, Elbows and Tees for UK Plumbers

Press-fit copper pipe fittings have transformed the way UK plumbers connect heating and hot water systems. Unlike traditional end-feed or Yorkshire fittings that require a blowtorch, flux, and solder, or compression fittings that rely on an olive and cap nut, press-fit systems use a dedicated press tool to permanently deform a stainless steel ring inside the fitting, creating a watertight joint in seconds. The Pegasus M-Profile system — compatible with Viega, Klauke, and most press tools on the UK market — is stocked across 15mm, 22mm, and 28mm in the full range of couplers, elbows, tees, reducers, and ball valves, all suitable for domestic heating, hot and cold water, and low-pressure commercial plumbing systems.

What Are Press-Fit Copper Pipe Fittings?

Press-fit fittings (also called pressfit or crimp fittings) use a pre-loaded O-ring inside the fitting body, compressed against the pipe wall when a jaw-type press tool is applied to the fitting collar. The O-ring provides the water-seal; the deformation of the collar locks the pipe in place mechanically. The system requires no heat, no flux, no solder, and no consumables beyond the fittings themselves.

The M-Profile (sometimes called M contour or M-Press) is the dominant press-fit standard in the UK and Europe. It is characterised by a distinctive M-shaped profile on the collar once pressed, produced by jaws with a matching M-profile geometry. M-Profile is the standard used by Viega (who pioneered press-fit technology), and virtually all UK press tools — including those from Ridgid, Klauke, Rothenberger, and Milwaukee — carry M-Profile jaws as standard for 15mm, 22mm, and 28mm copper.

Press-Fit vs Compression vs End-Feed: Which to Use?

Each connection method has its place on a domestic heating or plumbing job:

• End-feed/Yorkshire solder fittings — cheapest per fitting, permanent, ideal for concealed work. Requires soldering skills, a torch, and dry pipe. Not suitable where a heat source is restricted (e.g. near gas pipes, inside a confined cupboard).
• Compression fittings — no special tools needed, fully reversible. Preferred under sinks and behind appliances where future access is needed. Bulkier and more expensive than solder fittings; must not be over-tightened or the olive distorts.
• Press-fit fittings — fastest installation (a 15mm joint takes under 5 seconds once the tool is positioned), no flame, no flux, no debris. Permanent once pressed. The press tool represents the main capital cost, but for a plumber doing multiple joints per day, the labour saving is significant. Press-fit is also the safest method where heat is restricted — service valves on unvented cylinders, joints inside wall cavities, or near timber in a roof space.

Press-fit copper fittings are approved under BS EN 1254-7 (press connections for copper tubes) and are compatible with full system pressures typical of sealed central heating (1.5–3 bar working) and mains cold water. They are not suitable for natural gas or LPG pipework — always use approved gas press fittings for those applications.

Pipe Sizes and Where Each Is Used

The three core sizes in domestic UK plumbing and heating are:

• 15mm — the standard size for domestic connections: tap tails, radiator valves, branch connections, underfloor manifold spurs, and appliance isolation. The vast majority of domestic plumbing is in 15mm copper.
• 22mm — used for main runs: flow and return mains on a central heating system, primary pipe on an unvented cylinder, hot and cold supply mains before branching to 15mm, shower supply in high-demand properties.
• 28mm — primary circuit on larger systems: boiler flow/return on high-output combi or heat-only boilers, immersion heater flow/return on unvented cylinders (WRAS-approved systems), commercial domestic hot water loops. Also used for the primary circuit connecting a boiler to a cylinder in an indirect system.

Product Cards

Press Tool Requirements and O-Ring Identification

A press-fit system is only as reliable as the press operation. Key points:

• Tool calibration: Use a calibrated tool. Most manufacturers recommend annual service intervals. An under-pressed joint may appear sound but fail under system pressure.
• O-ring condition: Inspect the O-ring before pressing — it should be seated evenly in the groove with no nicks or flat spots. Fittings damaged in transit should be discarded, not pressed.
• Pipe preparation: Cut square (use a pipe slice, not a hacksaw where possible), deburr the internal and external edge, and clean any swarf or flux residue from the pipe end before inserting. Insertion depth markers on the pipe confirm full seating.
• Un-pressed fittings: If fitting is positioned but not yet pressed, the O-ring provides a temporary water-tight seal under low static pressure — but this is not reliable and must not be left. All fittings must be pressed before system pressure test.
• Leak indicator: Pegasus and other M-Profile fittings include an indicator window or tab that shows if a fitting has been pressed — check after commissioning and before burying in plasterwork.

Installing on an Occupied System

One of the strongest practical advantages of press-fit over solder is the ability to make joints on a system that cannot be fully drained or cannot be kept dry:

1. Drain as much of the affected section as possible. Isolate valves, open drain cocks, and use a wet/dry vacuum on open pipe ends to remove standing water.
2. Mop remaining water from within 50mm of the joint location — press-fit O-rings tolerate slight moisture but a standing body of water inside the fitting at the moment of pressing risks incomplete O-ring seating.
3. Insert pipe to full depth, confirm depth mark is flush with the fitting face, and press.
4. Pressure-test to 1.5× working pressure (typically 3 bar on a sealed heating system) before closing up.

Reducing Tees and Transition Fittings

The Pegasus M-Profile range includes reducing couplers and reducing tees for transitions between pipe sizes — for example a 22mm × 15mm reducer to drop from a main to a branch, or a 28mm × 22mm reducer at the cylinder header. Wall plate elbows (15mm × ½" female) provide the tap connection point where a surface pipe meets a faceplate — useful for kitchen mixer taps, washing machine and dishwasher supplies, and bidet connections.

Where Press-Fit Copper Beats the Alternatives

• Loft boiler installations — no heat risk to roof timbers or loft insulation.
• Kitchen and bathroom refits — fast turnaround on multiple joints, no smoke damage risk to new cabinets or tiles.
• Commercial landlord maintenance — a plumber with a press tool can commission a boiler swap, cylinder change, or radiator circuit in a fraction of the time of a solder job.
• Partial-drain repairs — making a repair on a system that cannot be fully drained without pulling the whole building off heat.
• Gas-proximity installations — under BS 6400 and the Gas Safety Regulations, naked flame within close proximity to gas pipework is restricted; press-fit eliminates the risk.

Related Products and Articles

If you are planning a heating or hot water project, these related articles and product categories are worth reviewing:

• Boiler Filling Loops — Types, Replacement, and How to Top Up Sealed System Pressure — how to manage sealed system pressure alongside new pipework.
• Panel Radiators and Column Radiators — BTU Sizing, Fitting, and Balancing — selecting and connecting radiators to the system you are pipeing.
• Boiler Servicing and Annual Central Heating Maintenance — adding inhibitor and descaler when commissioning a new circuit.
• 32mm and 40mm Push-Fit Waste Pipe Fittings — above-ground drainage to pair with sink and appliance supply work.
• Toilet Cistern Maintenance — Fill Valves, Flush Valves, and Siphon Replacement — cistern isolation and water supply connections.

Summary

Pegasus Pressfit M-Profile fittings offer UK plumbers the fastest, cleanest, and safest method of joining copper pipework across domestic and light commercial systems. Stocked across 15mm, 22mm, and 28mm in couplers, elbows, tees, reducers, wall plate elbows, and ball valves, the full M-Profile range is available from APM. All fittings are compatible with standard M-Profile press tools and carry BS EN 1254-7 certification for hot and cold water and central heating applications. Whether you are running a 15mm branch to a new radiator, commissioning a 28mm primary circuit on an unvented cylinder, or making a repair on an occupied heating system, press-fit copper eliminates the need for heat, flux, and solder — and gets you off site faster.

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APM Electricals
24 Western Avenue, Acton, London W3 7TZ
Phone: 020 8702 8080
Web: www.apmi.uk
Same-day collection available for West London trades.