Which blowtorch for soldering copper pipe?

Soldering a capillary joint is a heat-control problem, not a raw-power problem. The joint needs controlled heat around the fitting: lead-free solder flows at roughly 230-250 °C, the flux must not burn off, and the pipe must not overheat. A flame that is too small never gets the fitting there; a flame that is too fierce scorches the flux and blisters the paste before the solder moves.

That is why plumbers reach for a torch that holds a steady, aimable flame at the fitting mouth - not the biggest flame in the van.

EN417 cartridge torches are light, one-hand, instant-on with piezo ignition, and the cartridge is bought locally - no cylinder, no hoses, nothing pressurised in the post. For 15 and 22 mm capillary fittings, this is genuinely enough heat: the cartridge torch is the fastest tool to set up and the easiest to control around a joint.

The trade-off is endurance. A small cartridge can run out mid-job on a long run of fittings - keep a spare cartridge in the bag and you never notice.

The nozzle, not the torch body, decides whether the flame suits the job. A soldering nozzle concentrates a steady medium flame on the fitting; a spreader throws a wide, soft flame for heat-shrink; a fine flame is for precise small work. Fit the right nozzle to the cartridge and the torch behaves like a tool twice its price.

On a standard EN417 cartridge, the soldering nozzle is the one you want for pipework - match it to the fitting size, and if you are unsure, send us the fitting and we will confirm the nozzle.

Copper tube comes in three diameters a plumber meets most days: 15, 22 and 28 mm. Each wants a different amount of heat, because each has its own wall thickness and its own mass of fitting to bring up to temperature. Match the flame to that mass and the solder flows first time; guess and you either scorch the flux or stand there waiting.

Fifteen millimetre tube is the lightest work. It comes up to heat fast, so the danger is overshooting. Hold the torch back, keep the flame moving round the fitting, and feed the solder the moment the joint is up - a small, steady flame beats a big one on this size every time.

Twenty-two millimetre is the everyday domestic size and the middle of the road. It wants a soldering nozzle with a medium flame, played evenly around the fitting so the heat soaks in from all sides. Watch the flux turn glassy, then move.

Twenty-eight millimetre and above is where a cartridge torch starts to work. The fitting is heavier and the pipe pulls heat away quickly, so you hold the flame longer and move it more. You can still solder it with butane on a calm day, but this is the point where an oxy-fuel rig or a brazing nozzle begins to earn its keep.

A torch that is perfect for ten fittings can be wrong for two hundred. On intermittent work - a repair here, a new tee there - the butane cartridge torch is unbeatable. The piezo lights it in a second, it works one-handed, and it packs away with no hoses to coil and nothing to bleed.

A long run of 22 mm fittings is a different animal. You are on and off the flame for hours, and the cartridge is doing two jobs at once: heating the joint and reheating itself as the gas boils off. In cold weather the vapour pressure drops and the flame sags just when you want it strongest. Carry a spare cartridge, let the torch rest between fittings, and the run stays comfortable. If the work is genuinely continuous - a whole manifold or a full heating circuit - that is when a cartridge stops being the right tool and the oxy-fuel question comes back.

A draught does two things to a cartridge flame: it blows the heat sideways off the joint and it makes the flame flutter, so the heating is uneven. Outdoors, work with your back to the wind and cup the flame close to the fitting. Indoors, close the window and shut the door before you start - a cross-draught through a kitchen is enough to double the time a joint takes.

Tight spaces have the opposite problem. You cannot get the torch square on the fitting, so you heat one side and wait for the heat to creep round. That is when nozzle shape matters most: a compact flame that lets you get in close without burning the skirting board, the pipe clip or the cable behind. Plan the angle before you light, and clear anything that will not enjoy a flame.

Big runs of 28 mm and above, heavy fittings, or copper-to-brass work in cold weather can out-run a small cartridge. That is the moment for an oxy-fuel brazing set-up - and the moment the job stops being soldering and becomes brazing. Brazing runs hotter and needs the dedicated nozzle series, so read the brazing guide before you buy.

You know you have reached that point when the flame has been on the fitting for a minute and the solder still will not flow, or when the flux has blackened and the joint looks dull. Oxy-fuel brings the heat up fast and takes it away fast, so the fitting does not sit cooking while you wait. That work needs the dedicated oxy-acetylene welding nozzle series and the brazing nozzles - at that scale, soldering is over.

The fitting is what you are heating, but the pipe on both sides conducts that heat away - and towards whatever is touching it. Wipe the joint dry before you start, keep the flame moving, and never park it on one spot.

Before you light up, look past the joint. A soldering torch finds the joist above the floorboard, the plastic push-fit fitting a foot away, the lagging, the paint and the cable clip. Wet a rag and drape it over anything you cannot move; on a stud wall, slide a heat mat behind the pipe. The job is to heat the fitting, not everything near it - the blowtorch safety checklist runs through the rest.

The straightforward setup: the 1300°C EN417 cartridge head, plus a tip cleaner in the bag - a carboned nozzle is the usual reason a torch suddenly “doesn’t get hot enough”.

Technique in one line: clean the pipe, flux the joint, heat the fitting not the pipe, and feed solder where the pipe meets the cup. When the solder flows at the mouth of the joint, you are done. For the full sequence with the mistakes that ruin joints, see how to solder copper pipe with a blowtorch.

A cartridge flame covers a lot of joints for the gas it uses, and the gas is bought from the shop down the road rather than carried or posted. The real waste is not the gas you burn - it is the gas spent trying to heat a joint the nozzle cannot reach, or redoing a joint the flux scorched because the flame was too fierce.

That is why matching the nozzle to the fitting matters more than buying a bigger cartridge. A correctly sized EN417 cartridge head with the right nozzle gets a 22 mm joint to temperature in one pass, and one pass is the most efficient pass there is.

Butane cartridges: store cool, never pierce, check the EN417 valve seal before screwing on a nozzle or torch. Air torches involve no gas cylinder at all - and always check local gas-appliance rules before fitting any part (EU GAR / UKCA apply to gas appliances; our parts are spares).