DIY Home Repair: Sweating Copper Pipes

Home builders first started to use copper pipes for residential water systems in the late 1950s. Copper was used because of it's rot resistance and ease of use. This resulted in substantial savings on installation and labor costs.

Until the late 1970s, the solder that was used to make the connections in water systems was half tin and half lead. This presented a potential health risk because lead was slowly released into the water system. To make a bad situation worse, whole-house water softeners made the water corrosive, and aided the breakdown of solder.

Modern plumbers use solder that is 95 percent tin and only 5 percent lead. This makes copper a safe and inexpensive option for use in residential water systems. For the modern handyman, copper is a blessing. With some practice you can become quite competent at sweating it. "Sweating" is a soldering technique that creates strong joints in copper piping.
Remember: Safety is no accident! You should wear eye protection and fireproof gloves when you are soldering or working with flux. Flux is toxic, so extra caution is required. Also, keep open sleeves tightly closed if you are going to be working with overhead piping. We are going to be working with fire, so inspect the area that you're going to be working in. This is likely to be a tightly confined space. Sometimes you'll need to set up a fireproof heat shield between the solder joint and flammable material that is nearby.

Since some household appliances require a cold water supply to properly function, be sure to turn off any equipment that might be damaged by a loss of water. Ideally, you should do this at the breaker box. Boilers or other heating systems, evaporative (swamp) coolers, hot water heaters, and dishwashers are among the kinds of equipment that might be affected by cutting off the water supply.

When copper pipes are pushed together, there is a miniscule space between the two pieces. When the pipes are hot enough, and solder is applied to them, the solder melts. It is then drawn into the gap via capillary action. When the space is full and the heat is removed, the solder hardens and seals the gap, leaving a watertight joint.

Soldering pipes is both an art and a science. It becomes easier the more you get the hang of it. It is important to realize that you are trying to heat up the pipes, not the solder. The hot copper tubing should melt the solder.
You should practice on some spare parts until you get the feel for sweating copper tubing. Once you feel that you've got the hang of it, follow these instructions:

1. Remove any burrs that may reside on the inside and outside edges of the pipe. A deburring tool is recommended, and may be included as part of your tube cutting tool. Small burrs can cause many problems throughout the life of your plumbing system.
2. You should clean the outside of the pipe until it is bright and shiny. You can use a copper pipe cleaning brush, fine sandpaper, steel wool or emery cloth. If the copper isn't clean, the solder won't form a watertight seal.
3. Use a wire brush to clean out the inside of the fittings, where applicable.
4. Use acid-free flux or soldering paste on the outside of the male fitting and the inside of the female fitting. This will remove residue and prevent oxidation, which can be caused by heating the pipe up. If the pipe is oxidized, the joint might leak.
5. Push the pipes together until they are snug.
6. Unroll four inches of solder and straighten it. Use the roll or container as a handle when you're applying the solder.
7. Ignite your torch and apply the inner flame tip to the outer joint. Move the flame around, ensuring that you heat the entire overlapping area.
8. When the flux boils, Remove the heat. Apply the tip of the solder to the highest point, in the space where the two pipes meet. The solder should melt, and be sucked into the joint. Work quickly because the pipe's temperature will drop quickly. Keep pressing the solder into the crevice as it melts, until solder drips out of the bottom of the joint.
9. Optionally, you can use a damp rag to wipe the joint clean. Not only will this will give a your work a professional appearance, but it will result in a longer lasting joint, as it prevents corrosion over time.

Notes:
* Plan out your project beforehand whenever possible. Sweating pipes on the workbench is much easier than doing it all in a confined space.

* Make sure all of the joints will fit together before you work on them. Sometimes, a pipe may have been squished out of round, and it won't fit in the joint. In this case, cut a new piece and try again.

* Draining the water lines beforehand will make your job much easier. If you've shut off the water main, open all of the valves in the house, starting with the top floor and working your way down.

* Be sure to check your work for leaks after you're done.

* Try not to overheat the copper. This causes oxidization that will prevent the solder from bonding.

* If your repair was unsuccessful, your best bet is to cut out the joint and start with new parts.

* Use either lead-free or 95/5 solid-core solder- do not use acid-core solder.

* The pipes must be thoroughly dry or the solder won't bond properly.

* When you're done, let the pipes cool off naturally. Rapidly cooling pipes using water might damage the joint.

*Try not to use the torch directly on the solder or a surface that has been fluxed. Don't overheat the copper pipe. Look at the flame on the side of the pipe that is opposite the torch. When a green flame develops, the joint is ready to solder.

* If you are unable to stop the flow of water in the pipe that you're working on, you may not be able to get the pipe hot enough. Remove the crust from some white bread and stuff it into the pipe. This should stop the water for a few minutes. Afterwards, the bread will dissolve harmlessly, and it's easy to flush out. Toilet paper will work for this purpose as well.

* When you're working with couplings, elbows or tees, you should try to do all of the sweating at one time. Heat the fitting and quickly applying solder to every joint. If you need to reheat something, put a wet cloth over parts that have already been soldered.

* Try using different tips on your torch until you find the one that seems to work best for you. Ideally, the torch should heat the fitting as evenly as possible.

* Store your copper fittings in a plastic box with bits of newspaper. This will help keep it from getting damaged by moisture over time.

*If you are sweating a valve, make sure that it is in the open position. Otherwise, the heat will melt the internal seals of the fixture.