How to Sweat a Copper Pipe Fitting – A Simple Guide You Should Know

Sweating copper pipe fittings is a very basic procedure, but one which intimidates many people. While it will take some practice, you can sweat copper pipes.

Most homes use copper pipes for their plumbing needs. While a professional plumber can fit and install these pipes with relative ease, it is also possible for the weekend do-it-yourself homeowner to assembly copper piping. The critical area is in the fittings and joints.

These fittings must be sweated together using solder which bonds with the copper at a molecular level. Proper preparation can help insure a watertight fitting. Poor preparations or a rushed approach will result in leaks and potential damage to your home.

fitting copper pipe
Test fitting copper pipe – image by Scot

Before beginning to sweat copper pipe fittings you should consider your personal safety as well as the safety of your home. Always wear eye protection when sweating pipes.

You should also have a fire extinguisher at hand. Depending on what type of device you are using to heat the copper pipes the flame can reach temperatures in excess of 3,600 degrees Fahrenheit. These flames can and have resulted in home fires, so take care when working in close confines or near combustible materials.

Cleaning Pipes Prior to Sweating

The first step to preparing the pipe is to cut it to the proper length. This first step is critical and if done incorrectly can doom the project. Use a pipe cutter and work slowly. Do not attempt to cut the pipe all at once. This will result in the end of the pipe being distorted or warped. Once the pipe is cut, use a brush to clean away any spurs or rough areas on the pipe.

Once the pipe is smooth, use a dry cloth to remove any dirt, grease or debris. It is critical for the area to be as clean as possible to get a good bond between the two pieces of copper. Do not use the same piece of cloth for too long or you risk taking the dirt from one pipe fitting and transferring it to another fitting.

fitting copper pipe
Plumbing contractor works on the copper pipe domestic water system on a luxury custom home – image by Handy

Apply the Flux to the Copper Pipe

Use the small brush supplied with the flux to spread a thin layer of flux along the end of the pipe to be inserted into the fitting. Allow the flux to extend a quarter to half inch beyond where the fitting will reach. You want a good layer of flux on the pipe but there is no need for a thick layer.

After the flux is applied, slide the two copper pieces together. Use the flux brush to remove any excess flux which is pushed out from the fitting. This will save the flux for future use and will also make it easier to apply the solder when the time comes.

Heating the Pipe to Sweat the Fittings

Apply the heat to the fitting area. Be very careful if the pipe is against or near wood beams or floor joists. Attempt to heat the fitting evenly. At this stage you will need to watch the area and the copper very carefully. The copper will get shiny as it is heated. The copper will then begin to dull and the flux will sizzle and begin to smoke. This is a signal the fitting is ready for the solder to be applied.

Remove the heat and gently touch the solder to the pipe joint. The solder will melt and be pulled up into the fitting. Move the solder around the entire pipe joint to make certain all areas are filled. The solder will bond with the copper at a molecular level to make a solid and permanent bond.

Allow all fittings to cool before allowing water to enter the pipes. Once you have turned on the water supply to the new or repaired pipe you will need to allow the water to run in order to remove all air from the pipes. As the water flows through the pipes inspect all fittings for any leaks.

You should check for leaks with the water running as well as with the water turned off to allow the pipe to hold the maximum amount of pressure in order to check for any potential leaks.