Sweating Copper Pipe, Why sweat copper pipe

Sweating Copper Pipe speaks to how to sweat copper pipe and why sweat copper pipe.

The most common problem you will experience after sweating copper pipe is a leaking connection due to an improperly cleaned pipe or fitting. To prevent this, clean both with either a wire brush made for cleaning copper or a plumber’s cloth which is sandpaper with a fabric backing.

Clean the outside of the pipe slightly beyond the point where the fitting’s hub will terminate.

A new fitting does not arrive clean. It has an oil film that must be removed with a wire brush made to fit into its hub. Before you heat the pipe and fitting apply solder, brush a soldering paste on both the pipe and fitting. The paste allows the solder to flow properly. A tinning paste leaves a metal powder in the joint and allows the solder to flow even better.

Once you have applied paste to both the fitting and the pipe, sliding the fitting on the pipe. Wipe away any excess paste as not doing so may cause the solder to flow away from the fitting.

Now you are ready to heat the pipe and fitting. First, look at the work area. Can anything be harmed by heat or fire? If fire is a concern, you need to insert a fibreglass antiburn cloth to block the flames.

Apply heat first to the fitting and then to the pipe, alternating back and forth until both are hot enough to melt the solder. If you get the joint too hot, you will ruin the paste, and the solder will not flow. If the joint is not hot enough, nothing will happen. It takes some practice to determine how much heat you should apply in a given time.

Place something to catch any solder drips under the joint. Keep tapping the solder onto the joint until the solder starts to melt. Once the solder melts, let around ½ inch of solder flow into the joint and remove any excess solder.


Use a low temperature solder with a wide working range and a hard to burn tinning paste to aid soldering.

If water in a pipe has frozen, it may change the pipe’s outside diameter, and fittings may not slide on. You will have to cut the pipe back to where it has not frozen to get a perfectly round circumference for fittings. Sometimes however, you can use a tubing flaring tool to squeeze the pipe back to proper diameter for a short distance.

Solder will flow vertically upwards into a joint.

When cleaning copper, use plumber’s cloth which is pliable fabric backed sandpaper on a roll, or wire brushes designed to clean both the outside of a pipe and the inside of a fitting.

Get waterproof plumber’s cloth. It will not dissolve when wet, or contaminate the pipe or fitting. Wire brushes come individually or as an all-in-one cleaning tool. Keep both plumber’s cloth, open weave or solid and wire brushes handy.

Be aware that a fiberglass flame shield or piece of metal stops only the flames, it does not the heat from igniting flammable materials. To stop heat penetration, use a 1 lb thick concrete block.

Completion of sweating copper pipe.

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