Copper Pipe and Compression Fittings — End Feed, Solder Ring, and Pushfit Plumbing for UK Plumbers

Copper remains the default pipework material for UK domestic heating and water supplies. It lasts 50+ years, tolerates high temperatures and pressures, resists bacterial growth, and accepts four different jointing methods — compression, end feed solder, solder ring (Yorkshire), and press-fit. This guide covers the most common joining techniques, when to use each, sizing rules, and the hand tools you need to work copper confidently on a domestic installation.

Copper Pipe Sizes: What the Numbers Mean

UK copper pipe is sized by outside diameter (OD) to BS EN 1057. The common domestic sizes are:

• 8mm OD: Microbore central heating circuits, capillary connections to radiator valves — rarely used in new installations but common in older properties
• 10mm OD: Microbore central heating, icemaker/fridge supply lines, some underfloor heating circuits
• 15mm OD: Cold and hot water supplies to taps, showers, basins, WCs, radiator connections, and domestic gas (where copper is permitted)
• 22mm OD: Main flow and return runs in central heating, cold mains supply to combination boilers, hot water cylinder primaries, bath supply
• 28mm OD: Primary circuit flow and return on larger boilers, high-demand mains supply, circulation pump connections
• 35mm / 42mm OD: Commercial primaries and main building supplies — uncommon in domestic work

Wall thickness varies by grade: Grade X (heavy) is used for bending; Grade Y (medium) is standard for straight runs and is what you'll find in most trade packs. Grade Z (thin-wall) is only suitable for capillary jointing, not compression.

Compression Fittings: The Reliable, No-Heat Joint

Compression fittings grip the pipe mechanically using an olive (also called a ferrule or compression ring) that deforms onto the pipe as the cap nut is tightened. No flux, no heat, no solder. They are ideal for:

• Locations where a naked flame is unsafe (near timber joists, lagging, insulation, or gas meters)
• First-fix repairs where the system cannot be fully drained
• Connections to components with push-fit or compression ports (ball valves, stop taps, pressure reducing valves)
• Dissimilar metal connections where soldering would cause galvanic issues
• Student or less experienced installers — no soldering skill required

Type A vs Type B Compression

The two compression fitting standards used in the UK are:

• Type A (non-manipulative): The pipe is inserted without preparation — the olive slides over and grips the pipe wall. This is the standard type for domestic water and heating. Fittings are made to BS EN 1254-2.
• Type B (manipulative): The pipe end is flared or swaged before insertion, creating a tighter primary seal. Used in gas and some refrigeration applications — not typical for water or heating.

For water and central heating, all standard compression elbows, tees, couplings, reducers, and valves are Type A.

Making a Compression Joint — Step by Step

1. Cut square: Use a pipe slice (preferred) or pipe cutter to get a clean, square cut. A hacksaw leaves burrs that damage olives.
2. Deburr: Use the reamer or deburring tool on your pipe cutter. Inside burrs cause turbulence and erosion; outside burrs prevent the olive seating correctly.
3. Clean the pipe: Wipe with a dry cloth to remove swarf, flux residue, or moisture.
4. Assemble: Slide on the cap nut (thread facing the fitting), then the olive, insert the pipe fully to the stop inside the body.
5. Tighten: Hand-tight first, then one-and-a-quarter turns with a spanner. Mark the cap nut with a marker pen so you can see if it moves. Do NOT over-tighten — this splits the olive and causes leaks.
6. Test: Pressurise and check. If it weeps, one-eighth of a turn more maximum. Still leaking = disassemble, check olive seating, and reassemble.

PTFE tape on compression fittings: Not required on the olive — the olive creates the seal. PTFE tape on the cap nut thread adds slight lubrication and can make it easier to achieve a good nip, but it is not standard practice. Never wrap PTFE on the olive itself.

Compression Fittings on Plastic Pipe

Standard Type A compression fittings work on JG Speedfit, Hep2O, and other pushfit plastic pipe — but a plastic or metal insert (pipe support liner) must be fitted inside the pipe end before assembly. Without a liner, the olive crushes the soft plastic bore, causing flow restriction and potential long-term leaks. Most pushfit manufacturers sell matched compression olives and liners; alternatively use brass olives and universal liner inserts.

End Feed Fittings: The Tradesperson's Standard

End feed (also called "capillary" or "Yorkshire-style") fittings are the fastest, neatest, and most economical permanent joint for copper pipework. The fitting has a plain socket — no pre-applied solder. You apply flux, heat the fitting, and feed solder wire into the mouth of the joint until it wicks in and forms an even ring around the full circumference.

Why Tradespeople Prefer End Feed

• Cost: End feed fittings are significantly cheaper than solder ring or pushfit equivalents — typically 30–50% less per fitting
• Speed: An experienced plumber can make 60–80 joints per hour with a gas torch
• Reliability: A correctly made end feed joint is stronger than the pipe itself; the capillary action fills the entire annular gap
• Compact profile: End feed fittings sit flush against the pipe — less bulk in confined spaces than compression

Making an End Feed Joint

1. Cut and deburr as for compression (pipe slice preferred).
2. Clean both surfaces: Use wire wool or emery cloth on the pipe end (last 20mm) and the inside of the fitting socket until bright. Any oxidation or contamination prevents solder adhesion.
3. Apply flux: Smear a thin, even coat of flux paste on the pipe end and inside the socket. Use a lead-free flux compliant with BS EN 29454-1. Apply only where solder must flow — excess flux on surrounding pipe causes corrosion staining.
4. Assemble: Push pipe fully home into the fitting socket. Hold or support so it cannot move during heating.
5. Heat: Apply the torch flame to the fitting body — not the pipe. Heat the heaviest part of the fitting (elbow back, tee centre) and let heat conduct to the solder area. The fitting should be hot enough that solder melts on contact; if you heat the pipe end directly you can overheat the joint and boil off the flux before solder wicks in.
6. Feed solder: Touch 0.5mm lead-free solder wire (BS EN ISO 9453 grade S-Sn97Cu3 or similar) to the mouth of the joint. When the temperature is right, the solder flows in immediately and draws around the full circumference. Feed until a bright, even ring appears at the joint mouth — typically 10–20mm of wire for a 15mm joint, 25–35mm for 22mm.
7. Wipe and cool: Wipe with a damp cloth to remove excess flux. Allow to cool naturally — do not quench with cold water (thermal shock can crack the solder).
8. Inspect: A complete fillet ring around the full joint mouth is required. Dark patches or gaps indicate cold spots — the joint may leak under pressure.

Flux Selection: Lead-Free and WRAS Approved

All flux used on drinking water pipework must be:

• Compliant with BS EN 29454-1 Type 1 (no chloride-based flux on copper water pipes)
• WRAS approved for potable water use (check WRAS Product Approval Scheme list)
• Lead-free — COSHH regulations and water quality regulations prohibit lead solder and flux on domestic hot and cold water

Fernox Flux and Safetyflex are commonly used; avoid rosin-based electrical flux entirely — it does not provide adequate sealing properties for plumbing joints.

Solder Ring Fittings (Yorkshire Fittings)

Solder ring fittings have a pre-loaded ring of solder inside each socket. The jointing procedure is identical to end feed, except:

• No separate solder wire is required — the correct amount is already in the fitting
• When correctly heated, a bright ring of solder appears at the joint mouth confirming full wicking
• Slightly more expensive than end feed, but reduces waste and is useful when working overhead or in awkward positions where feeding wire is difficult

Solder ring fittings are also safer for apprentices — there's no risk of using too much or too little solder, and no separate wire to manage with a hot torch in hand.

Pushfit Plumbing: JG Speedfit, Hep2O, and Polyplumb

Plastic pushfit systems use polybutylene (PB) or cross-linked polyethylene (PEX or PERT) pipe with proprietary fittings that grip via a collet and O-ring. No tools, no heat, no flux — pipe pushes in and is held under pull-out force by a ring of stainless steel teeth.

Advantages

• No naked flame — safe in loft spaces, timber floors, stud walls
• Faster than copper soldering for long runs
• Demountable — pipe can be released by pressing the collet ring
• Flexible pipe tolerates small building movement without cracking

Limitations

• Higher material cost than end feed copper — especially since 2025 JG Speedfit price increases (+42%)
• Not suitable for continuous temperatures above 80°C (check manufacturer rating — most are rated to 70°C service)
• Fittings cannot be used on coiled copper or chrome pipe without adapters
• Building regulations require pushfit pipe to be clipped at shorter intervals than copper (typically every 300mm horizontal / 500mm vertical for PB pipe)
• Pipe must be inserted fully — partial insertion is the most common cause of pushfit joint failures. Use the depth gauge marker and always check the mark is flush with the fitting face

Transition Fittings: Copper to Plastic

Mixing copper and plastic pipework in the same system is common — for example, copper main runs with plastic branches to individual appliances, or plastic first-fix with copper connections to boilers and cylinders. Use purpose-made transition fittings with a copper male compression tail on one end and a pushfit plastic socket on the other. Never use standard brass compression fittings directly on plastic pipe without inserting a pipe support liner first.

Bending Copper Pipe

Copper can be bent without fittings using a pipe bender, which is faster and neater than installing an elbow fitting. For 15mm tube, a hand-operated bending machine (rotary bender) is standard. For 22mm and 28mm, a hydraulic bender is more practical.

• Minimum bend radius: Typically 3–4× pipe diameter for Grade Y tube — tighter bends cause pipe walls to flatten (ovalling), restricting flow
• No fittings advantage: Fewer joints = fewer potential leak points, faster installation, and a cleaner finished appearance
• Marked bends: Mark the pipe at the tangent points before inserting in the bender — the former on a rotary bender should be centred on your target bend point

Common Compression Fittings: What's in a Trade Pack

Standard copper compression fittings you'll use on every domestic job:

Fitting	Common Sizes	Use
Straight coupling	15mm, 22mm	Join two pipe lengths end-to-end
Reducing straight coupling	22mm×15mm, 15mm×10mm	Step down between pipe sizes
Equal elbow (90°)	15mm, 22mm	Change direction — use where bending isn't practical
Equal tee	15mm, 22mm	Branch a new supply from an existing run
Reducing tee	22mm×15mm×22mm, 22mm×22mm×15mm	Branch 15mm service off a 22mm main
Male iron (BSP male)	15mm×½", 22mm×¾"	Connect to female threaded components (boiler connections, valves)
Female iron (BSP female)	15mm×½", 22mm×¾"	Connect to male threaded components (tap tails, pump unions)
Tank connector	22mm, 28mm	Through-hole fitting for cold water storage tanks and cylinders
Stop end (end cap)	15mm, 22mm	Cap off redundant pipe — testing or decommissioning

Pipe Sizing for Common Domestic Applications

Correct pipe sizing prevents flow noise, poor pressure at outlets, and velocity-induced erosion:

• Cold mains supply to combination boiler: 22mm recommended. 15mm is marginal if the mains pressure is below 1.5 bar or the run exceeds 3m.
• DHW outlets (basin, bath, shower) from combination boiler: 15mm (short runs under 3m). If running a shower from a combi over 6m from the boiler, upsize to 22mm to minimise friction loss.
• Radiator branch connections: 15mm standard. Use 22mm lockshield/radiator valves on large radiators (>2000W output).
• Central heating flow and return: 22mm for up to ~8 radiators on a standard domestic system. Larger systems (10+ rads, larger boilers) should use 28mm primary circuit.
• Hot water cylinder primaries: 22mm minimum; 28mm for high-output boilers and large cylinders.

Water Regulations and WRAS Compliance

All fittings used on cold water supplies must comply with the Water Supply (Water Fittings) Regulations 1999 (England/Wales), Water Byelaws 2004 (Scotland), or equivalent (Northern Ireland). In practice:

• All fittings in contact with potable water should be WRAS approved — check the product datasheet
• Lead and lead-alloy fittings are prohibited on domestic cold water (Water Fittings Regulations Schedule 2)
• Lead-free solder and WRAS-approved flux must be used on all hot and cold domestic water connections
• Dezincification-resistant (DZR) brass is required for hot water fittings and where the local water chemistry (low pH, high chloride) causes standard brass dezincification — check your local water company's hardness and pH data

Isolating Sections: Ball Valves and Stop Taps

Every supply branch to an appliance or group of appliances should have an accessible isolation valve. The two standard options:

• 15mm full-bore ball valve (quarter-turn lever): The preferred modern type — opens fully with a quarter turn, low flow resistance, easy to operate and to see whether it's open or closed from the lever position
• Screw-down stop cock (BS 1010): Traditional brass crutch-head or square-head tap — still widely installed, but higher flow resistance and harder to operate than a ball valve. Required in some situations (under kitchen sink per water regulations for servicing the cold supply)
• Mini isolating valve (slotted head): Compact inline isolation for individual appliances — operated with a flat-head screwdriver. Used for toilet cisterns, basin taps, and washing machine supplies. Not full bore — not suitable for high-flow applications

System Commissioning: Pressure Testing and Flushing

Before handover, all copper pipework must be pressure tested and flushed:

• Cold water pressure test: Test at 1.5× operating pressure for a minimum of 1 hour with no visible leaks or pressure drop
• Central heating pressure test: Fill and pressurise to 1.5 bar (cold), check all joints visually. For new installations, BS 7593 requires a hydraulic test at 1.5× maximum working pressure for 30 minutes
• Chemical flush: BS 7593 requires flushing with a system cleaner (such as Fernox F3 or Sentinel X300) before filling with inhibited water (Fernox F1 or Sentinel X100). This removes flux residue, swarf, and manufacturing oils that cause corrosion and premature pump/valve failure
• Inhibitor dose: Follow manufacturer's dosing chart — typically 1 litre of inhibitor per 100 litres of system volume. Record the product and batch on the boiler commissioning record

Cross-References

• Flexible tap connectors and isolation valves: see Article #247
• Central heating inhibitors and magnetic filters: see Article #238
• Thermostatic mixing valves: see Article #239
• Wet underfloor heating systems (copper manifold connections): see Article #229
• Hot water cylinders and unvented systems: see Article #228