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19 September 2003

Cutting and Soldering Copper Pipe

Excerpted from Millard Lumbar, Inc. series "How to Work With Copper Pipe"

Cutting Copper Pipe

You can cut copper pipe with a regular hacksaw or a copper tube cutter (Fig. 3). Although both will make a satisfactory cut, the tube cutter ensures a square cut every time.

Use a jig or miter box when you're cutting copper pipe with a hacksaw. This helps to ensure a square cut in the pipe.

You can make a jig from a wooden board or block with a vee notch sawed out to hold the pipe in place.

A slot in the jig will guide the saw at right angles to the vee notch, making it easy to hold the pipe while cutting and helping ensure a square cut.

When using a pipe cutter, hold the copper tubing in place with a pipe vise or some other holding device.

After making the cut, remove the burrs inside the pipe with a half-round file. A pipe cutter usually leaves more burrs in the pipe than a hacksaw.

When cutting pipe for a specific run, be sure to make allowances for the distance of pipe that fits into the fittings. Also, remember to add the extra length the fittings will give the entire run of pipe. Figure about 1/2" for each fitting.

Figure 4 - Spread flux evenly on the cleaned end of the copper pipe.

Figure 5 - Rub flux into the cleaned fittings.

Figure 6 - Place the fitting on the pipe in its final position, rotating the joint several times.

Figure 7 - Use a propane torch to apply heat for soldering.

Sweating a Joint in a Copper Pipe

After you've cut the copper pipe to the proper length, clean the end of the pipe with a 4-in-1 tool. Clean the area to be inserted in the fitting until it is bright all around. You can also use a separate brush, fine sandpaper or steel wool.

If you're using the 4-in-1 brush, slide the pipe inside the brush. The standard 4-in-1 tool will clean both 1/2" and 3/4" pipe and fittings. Be sure you are using the right size. Turn the tool back and forth until the pipe is bright. You can also hold sandpaper or steel wool around the pipe with light pressure. Then turn the tube back and forth several times.

You must also clean the inside of all fittings. You can use the 4-in-1 tool, brush, steel wool or sandpaper. Take the time to clean them thoroughly. Debris or foreign matter left in the pipe causes a poor seal.

Next, apply a light coat of soldering paste or flux to the cleaned end of the copper pipe (Fig. 4). Use a flux brush, an old toothbrush or a wooden paddle for spreading the flux.

Flux or soldering paste ensures a firm bond between the copper and the solder.

Also apply flux to the inside of the cleaned fittings (Fig. 5). Use a flux brush, wooden paddle or toothbrush to apply the soldering paste.

The flux or soldering paste will keep the copper from oxidizing when heated.

Never use acid core solder for sweating copper pipe.

Place the copper fitting on the pipe only after it is thoroughly cleaned and coated with soldering paste (Fig. 6). When the fitting is firmly in place, rotate both the pipe and the fitting several times to spread the flux evenly.

A propane torch is an ideal tool for sweating copper pipe. If you look at the flame of a propane torch you will notice there is a lighter blue, well-defined flame in the middle of a darker blue flame. The tip of this light blue flame is the hottest part of the flame (Fig. 7).

Play the flame along the fittings and the pipe to bring them up to soldering heat. Then concentrate the heat in the middle of the fitting. The light blue flame should be just touching the fitting. You can do both ends of the fitting at the same time by heating in the middle like this.

Do not apply the heat directly to the solder or the area that has been fluxed. Do not overheat the copper pipe. If you look at the flame on the side of the pipe away from the torch, you may notice a green flame develop. This means the fitting is ready to solder. Another way to tell is to touch the solder to the hot pipe. If the solder melts and begins to run, the pipe is at soldering temperature.

Remove the flame from the pipe and apply the solder to the pipe where it joins the fitting. The solder will flow into the fit. Keep melting the solder until it appears completely around the fitting. The old saying, "If a little is good, then a lot is better," does not apply here. Excess solder can run down inside the pipe, causing a restriction or even a blockage.

Many codes now require lead-free or nearly lead-free solder to be used for water supply lines. Check with your local code to be sure. Never use acid core solder for sweating copper pipes. Use either lead-free or 95/5 solid-core solder.

If you are soldering both sides of a coupling or elbow or three sides of a tee, do it all at the same time. Heat the fitting and then quickly apply solder to all the joints. If you have to reheat a joint on a fitting, place a wet cloth on any nearby joints that have already been made. This can avoid damaging these nearby joints. You can experiment with different tips on your propane torch until you find the one that spreads the heat evenly along the pipe you are using.