Design & DIY

How to solder copper pipe

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There’s no reason an average Joe Plumber can’t match a pro in the art of soldering copper pipe. Those new to the task tend to over-apply the solder, coating pipe in unsightly silver gobs and telltale trickle marks. To improve your technique, try these tips for copper connections that will make any pipesmith proud.

Dry: Water in the pipe is your enemy. It will keep the pipe too cool for solder to stick, and turns to steam when heated, creating enough pressure to force fresh solder from the joint. After draining the line, stuff balled-up fresh white bread (without crusts) in the pipe to dam 
a persistent trickle (it will flush from the system when you’re done).

Scour: Molten solder flows best over clean, fluxed copper. Use emery cloth to clean tarnish off the pipe and the inside of the fitting until both shine like a new penny, before applying flux.

Heat: Upgrade from a propane torch to a more powerful methylacetylene-propadiene, or MAPP, gas torch. MAPP torches burn hotter, which greatly speeds up the job.

Melt: Molten solder flows towards heat, so play the flame over the fitting, not the pipe. A little after the flux sizzles, remove the flame and touch solder to the rim of the fitting—it will be sucked straight into the joint. Don’t leave the flame on the fitting too long or the solder will run back out, leading to excess globs.

Inspect: Wipe away surplus solder with a damp cloth (being careful not to burn yourself), then check all sides of the connection with 
a small mirror. Your goal is a thin, continuous ring of solder spread evenly around the joint. Practice on scrap pieces at the workbench and you’ll soon produce perfect joints every time.