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Using Flux
It’s easy to forget about flux, but it’s essential to a proper solder. Flux cleans the surfaces to be soldered, helps the solder flow, and creates a stronger bond.
Tinning flux is a step up from basic soldering flux. It contains a bit of silver solder powder that melts when heat is applied. The resulting thin layer of solder helps ensure a leakproof joint. Tinning flux is available at most hardware stores and home centers and only costs a little more than standard flux.
Means suggests taking time to examine your flux to ensure it hasn’t picked up any grit from the workspace. Flux with dirt or debris in it can cause poor distribution of the solder.
“Don’t let fluxed fittings or pipe set around for too long,” he says. “The resulting oxidation can cause issues. Always wipe excess flux and solder off with a damp rag. If you end up with an unsightly ball of solder on the joint, you can hit it quickly with the flame to soften and wipe it away. Don’t burn yourself here!”
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Keep Pipes Dry When Soldering
One of the most essential parts of repairing copper pipe is draining the system.
Soldering a joint in pipes that contain even tiny amounts of water is nearly impossible. Most of the heat from the torch goes into turning the water to steam, so the copper won’t get hot enough to melt the solder.
Unfortunately, it’s common to find a small amount of water in a pipe system even after you drain the pipes. Back when I learned how to solder, I was taught to jam white bread into the pipe.
“White bread is an old trick that does come in handy in a pinch,” Means says. “A small amount of white, not wheat, bread inserted into the pipe will help to stop a trickle of water. Just be sure to clean your aerators afterward if working near a fixture.”
While Means is familiar with these older techniques, there are better options these days.
“There are devices known as Jet Swets, which are rubber stoppers that are inserted into the pipe with a cord or stem,” he says. “They expand to seal off the flow of water and can then be pulled out once the sweat joint is made.”
Frequently Asked Questions
What tools do you need to solder copper pipe?
A cleaning brush, torch, flux and solder. Optional materials include a heat shield and water blocker.
Why does my solder keep turning into a ball?
“If your solder is turning into a ball, the pipe or fitting may not be hot enough,” Means says.
“Always start by heating the pipe near the joint first, then move the heat to the fitting. Test for the right amount of heat by touching the solder to the side of the joint opposite of the heat. The solder should melt and flow around the fitting. Then, remove the heat and touch the solder to the side of the joint that you were heating. Do not try to apply the flame directly to the solder.”
Can you overheat copper pipe when soldering?
Yes. “If the fitting begins to turn black and sooty, you have probably gone too far and cooked all of the flux out of the fitting,” Means says. “You will want to re-clean and flux the fitting and pipe again (once cooled).”
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