Short definition
A propane torch is a handheld torch fed from a 14- or 16-ounce disposable cylinder, used to heat copper fittings to solder-melt temperature. Propane runs about 3,600°F at the flame tip — plenty for any residential copper joint. MAP-Pro (the yellow cylinders) runs hotter and works faster on 3/4-inch and larger pipe.
What it is
Most homeowner propane torches are Bernzomatic-style: a brass torch head (5,000 to 20,000 BTU output) that screws onto a 14.1-ounce cylinder. Pro turbo torches push 50,000 BTU and heat large copper faster. Self-igniting heads use a piezoelectric striker; experienced trades carry a separate spark lighter as backup because piezo igniters fail.
Two fuels are common. Propane (blue or gray cylinder, ~3,600°F) is the standard. MAP-Pro / MAPP-substitute (yellow cylinder, ~3,700–3,800°F) is a propylene/propane mix sold as a replacement for true MAPP gas (discontinued in 2008). MAP-Pro heats faster on 3/4-inch and larger pipe; on 1/2-inch, propane is fine. Both work for residential copper. Lead-free solder (95/5 tin-antimony) melts at about 450°F — well below either flame.
The technique is to heat the fitting, not the pipe. The solder should melt on contact with the heated fitting, not the flame. This is the “bring the heat” rule from trade training.
Why it matters to a homeowner
A torch is the cheapest path to permanent copper joints — $30 for a torch head and a cylinder, plus solder and flux. The risk is fire. Soldering near framing, insulation, or a vapor barrier has been a documented ignition source for attic fires in PNW homes. Three rules keep this safe:
- Use a flame shield between the joint and any combustible surface. Always.
- Keep a pressurized water spray bottle and a fire extinguisher within arm’s reach.
- Do a fire-watch for 30 minutes after the last solder pass — wood smoldering in framing can ignite later, not while the torch is running.
If the choice between sweating and a press-fitting joint is open, press is now standard practice in occupied-home remodels because the fire risk is zero. Torch work has not gone away, but its share of WA repipe jobs is shrinking.
Common variants and not the same as
- Propane vs. MAP-Pro. Propane is the standard; MAP-Pro is hotter and slightly more expensive. Both work for residential copper.
- Propane torch vs. oxyacetylene. Oxyacetylene burns near 5,500°F — for brazing copper above the soft-solder range, or steel work. Pro tool, not homeowner.
- Self-igniting vs. separate striker. Piezo igniters fail more often than steel strikers; carry a backup.
Common failure modes
- Solder won’t flow. The joint isn’t hot enough. Heat the fitting, not the pipe — solder should melt on the fitting.
- Burned flux. Black residue means too much heat too long. Wipe off, re-flux, retry. Lead-free flux is more sensitive to overheating than legacy lead-flux was.
- Pinhole in cylinder. Stored near heat or damaged. Discard at a hazardous-waste site, not in trash.
- Fire. Most common cause of soldering-related insurance claims. Flame shield, water bottle, fire-watch.
Washington note
Soldering near framing in a remodel triggers WA-amended UPC requirements for fire-blocking and intumescent firestopping at penetrations. PNW fire marshals’ incident logs list “soldering” as a residential ignition source. In a wood-framed home with vapor-barrier insulation — most of pre-1990 Seattle and Tacoma — the fire-watch rule is not optional. If a contractor proposes soldering inside finished walls without fire-blocking or shielding, that’s a yellow flag. Either ask for press fittings or confirm written fire-watch protocol. Reasonable plumbers will not push back on this.