Soldering Copper Pipe Fittings: Solder Ring, End Feed, and Capillary Joint Guide

Capillary soldering is one of the fundamental skills of the plumbing trade. Despite the rise of push-fit and press-fit alternatives, soldered copper joints remain the preferred choice on many commercial projects, high-temperature systems, and anywhere a permanent, clean-looking joint is required. This guide covers the two main types of capillary fitting — solder ring (Yorkshire) and end feed — and takes you through the correct technique for making leak-free joints every time.

Solder Ring vs End Feed: What's the Difference?

Both types create a joint using the same capillary action principle: heat causes solder to flow into the narrow gap between the pipe and fitting, forming a watertight seal when cooled. The difference is where the solder comes from:

• Solder ring fittings (also called Yorkshire fittings after the original brand) contain a pre-formed ring of solder inside the fitting. Apply heat, and the solder melts and flows automatically — no separate solder wire required. Faster on site, harder to over-apply.
• End feed fittings contain no solder. You feed wire solder into the mouth of the fitting while applying heat. Requires more skill to judge the right amount, but significantly cheaper per fitting — often 30–50% less than solder ring equivalents.

For straightforward domestic work, solder ring is popular because it's more forgiving. For commercial volume work or where cost control matters, experienced plumbers use end feed and carry their own solder wire.

See also: Compression vs Push-Fit vs End-Feed Fittings for a full comparison of joining methods, and Copper Press-Fit Fittings if you want a no-heat alternative to soldering.

Tools and Materials You Need

Essential Tools

• Blowtorch — propane or MAPP gas. MAPP burns hotter (~2,020°C vs ~1,980°C for propane) and is preferred on larger bore pipe (22mm+) and in cold environments where pipe acts as a heat sink. A trigger-start torch with a swivel head is easiest on site.
• Pipe cutter — a wheel cutter gives a square, burr-controlled cut every time. A hacksaw is acceptable but requires deburring.
• Deburring reamer or half-round file — essential. Any burr left inside the pipe will trap flux and cause joint failure.
• Pipe cleaning cloth or wire wool — clean both pipe ends and fitting sockets before fluxing.
• Flux brush — for applying flux evenly.
• Heat mat or shield — mandatory near joists, floor boards, or any timber. Use a mineral wool heat mat behind the joint whenever working close to structural timber.

Consumables

• Lead-free flux — use only flux approved to BS EN 29454-1 / BS EN ISO 9454. Acidic flux (plumber's flux paste) is suitable for domestic copper to copper joints. Do not use acidic flux on dezincification-resistant (DZR) fittings or stainless — use a specific DZR/stainless flux.
• Lead-free solder wire (for end feed) — 95/5 tin/antimony or 99.9% tin alloy, to BS EN ISO 9453. Lead-free has been mandatory for potable water systems in the UK since 1999 (Water Supply Regulations 1999, Reg 4).
• Damp cloth or wet rag — to wipe excess flux and solder immediately after making the joint, before it cools completely.

Step-by-Step: Making a Capillary Joint

1. Cut the Pipe Squarely

A wheel cutter gives the cleanest cut. Tighten one turn at a time as you rotate — forcing the wheel creates a ragged edge and work-hardens the pipe end, making it harder to push into the fitting. The pipe should enter the fitting socket with hand pressure and sit fully home against the internal stop.

2. Deburr Inside and Out

Use the reamer built into your pipe cutter or a half-round file to remove the internal burr. Wipe away any swarf. Any material left inside the pipe will be swept into the system when water flows — and can damage pump impellers or ball valves downstream.

3. Clean the Mating Surfaces

Using fine wire wool or emery cloth, clean the outside of the pipe end and the inside of the fitting socket until both surfaces are bright copper. This is the step most beginners skip and most joint failures trace back to. Oxidation, oil from handling, or any contamination prevents the solder from bonding. Clean 10–15mm back on the pipe from the end — further than the socket depth.

4. Apply Flux

Apply flux paste to both surfaces — the pipe end and inside the fitting socket. Flux does two jobs: it prevents re-oxidation during heating, and it lowers the surface tension of the molten solder so it flows into the joint by capillary action. A thin, even coat is sufficient; excess flux burns in the joint and leaves voids.

Push the pipe fully home into the fitting socket. Twist slightly to distribute the flux evenly.

5. Protect Nearby Materials

Position a heat mat behind any timber, plasterboard, or other combustible material. Even if you think the structure is a comfortable distance away, use a mat — copper conducts heat rapidly along its length, and a joint 100mm from a joist will heat that joist. This is a Building Regulations and insurance requirement on all notifiable work.

6. Apply Heat

Play the flame around the fitting body — not just one spot and not directly at the flux. Move the torch in small circles around the circumference of the fitting. The goal is to heat the fitting and pipe end uniformly so the solder flows all the way around the joint.

Temperature cues:

• Flux will begin to bubble and spit — this is normal, keep heating
• The flux changes from white to straw/brown — getting close
• Touch the solder to the joint (away from the flame) — if it melts on contact, the fitting is at temperature
• On solder ring fittings: a bright ring of solder will appear around the mouth of the socket when the joint is made

Never apply the flame directly to the solder. The fitting must be hot enough to melt the solder, not the flame.

7. Feed Solder (End Feed Fittings)

Touch the solder wire to the joint at the edge of the socket — not into the flame. If the fitting is at temperature, the solder will be drawn in immediately by capillary action. Feed smoothly until a bright ring appears all the way around the joint mouth. On 15mm fittings, this takes approximately 8–10mm of solder wire; on 22mm fittings, 12–15mm.

Remove the flame as soon as the ring is complete. Continue to hold the solder wire at the joint for a moment — residual heat will draw in a little more if any voids remain.

8. Wipe and Inspect

While the joint is still hot (but solder has solidified slightly — grey, not shiny), wipe around the joint mouth with a damp cloth to remove excess flux and smooth the solder ring. This makes inspection easier and prevents flux residue from corroding the copper over time.

A good joint shows:

• A complete, even ring of solder visible around the whole socket mouth
• No drips or blobs (excess solder that didn't enter the joint)
• No discolouration or burning of the flux beyond the joint area

Let the joint cool completely before applying any mechanical stress. Do not quench with cold water — thermal shock can crack the joint.

Common Faults and How to Avoid Them

Pipe Sizes and Solder Quantities (End Feed Reference)

Gas Pipework: Soldering Rules

For natural gas and LPG pipework, soldered copper is permitted under BS 6891 (domestic installations up to 35mm) and IGE/UP/2 (industrial) but with stricter requirements:

• Only end feed fittings are permitted — no solder ring/Yorkshire fittings on gas. The pre-formed ring does not guarantee a void-free joint as required by Gas Safety (Installation and Use) Regulations 1998.
• Joints must be made with 95/5 tin/antimony solder — not tin/copper or silver-bearing alloys (unless specified by the fitting manufacturer).
• All gas capillary joints must be visually inspected and the system tightness-tested to BS 6891 Section 8 after installation. See our guide to Pressure Testing Plumbing and Heating Pipework for full tightness testing procedure.

Working on Live Systems: Draining and Drying

The most common cause of soldering failure is attempting to make a joint with water in the pipe. Even a small amount of water will prevent the fitting from reaching soldering temperature — the water absorbs heat faster than the torch can supply it, and the solder will never flow properly.

Before soldering on any existing system:

1. Isolate the supply (see isolation valve guide)
2. Drain down as much of the section as possible
3. Open the lowest drain cock and a high-point air vent to fully drain
4. Use a dry cloth pushed into the pipe end to absorb residual moisture
5. For sections that can't be fully drained, stuff white bread (crumbs removed) into the pipe — it holds back moisture during soldering and dissolves harmlessly when water is restored

Dezincification-Resistant (DZR) Fittings and Flux Compatibility

In areas with aggressive water (hard water, chlorinated supplies, coastal areas), DZR brass fittings are specified instead of standard brass. DZR fittings are marked with a triangle symbol. Standard acidic flux is not compatible with DZR or gunmetal fittings and can cause long-term corrosion. Use only flux marked for DZR/potable use on these fittings.

Most high-quality capillary fittings sold for potable water systems are now manufactured in DZR brass as standard — check the product marking if in doubt.

Regulations and Compliance

• Water Supply (Water Fittings) Regulations 1999 — all fittings and materials in contact with potable water must be compliant with WRAS (Water Regulations Advisory Scheme). Lead-free solder is mandatory. Fittings must be WRAS approved or meet the specifications of the Water Regulations.
• BS EN 1254 — covers capillary and compression fittings for copper tube. Part 1 covers capillary fittings with solder ring or end feed sockets.
• Part P (Building Regulations) — work on hot and cold water systems does not require notification under Part P (which covers electrical work). However, work on unvented hot water cylinders requires G3 qualification. See our Unvented Cylinder Guide.
• Hot work permit — on commercial or managed premises, any open-flame work typically requires a hot works permit, fire watch during the work, and a 60-minute fire watch after finishing. Check with the site manager.

Related Products

APM stocks a full range of capillary fittings for domestic and commercial plumbing:

• Embrass Peerless Atomic end-feed fittings — 8mm to 54mm, all common configurations (straight couplings, elbows, tees, reducers, male/female adapters). Manufactured in DZR brass to BS EN 1254-1. Among our top-selling products by unit volume.
• Solder ring (Yorkshire-type) fittings — available in 15mm and 22mm common configurations for domestic work
• Lead-free solder wire — 95/5 tin/antimony, 3.25mm diameter, suitable for all potable water and gas applications
• Flux paste — BS EN ISO 9454 compliant, brush applicator

Browse the full range of copper fittings and soldering materials in our End Feed Fittings collection.

Shop Embrass Peerless Atomic End Feed Fittings at APM

Atomic 15mm End Feed Coupler (from £0.18)

Atomic 15mm End Feed Elbow (from £0.29)

Atomic 22mm End Feed Coupler (from £0.55)

Atomic 22mm End Feed Elbow (from £0.76)

Key Takeaways

• Clean copper is the foundation of every good solder joint — skip the wire wool stage and the joint will fail
• End feed is cheaper per fitting; solder ring is faster and more forgiving on site
• Water in the pipe is the leading cause of joint failure — always drain and dry before soldering
• On gas pipework, only end feed is permitted — no solder ring fittings
• Use lead-free solder only — it's been a legal requirement on potable water since 1999
• Always use a heat mat when working near timber or other combustibles

For trade advice and orders, contact APM Electricals at 1 Hartington Road, Southall, UB2 5AL or call 020 8574 3233.