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How To Solder Copper Pipes

When copper pipes are joined with fittings, there is a very small gap between the fitting and the pipe. When the pipe and fitting are heated, and solder is touched to the pipe, the solder melts and is drawn up into the gap through capillary action. Once the gap is filled, and the heat removed, the solder forms a seal and makes a watertight joint.

Caution: Please read our safety information before attempting any testing, maintenance or repairs. Wear eye protection and gloves when soldering and when working with flux. Flux is a toxic substance. Some equipment may rely on a cold water supply. Take appropriate steps to shut down any equipment that may be adversely affected by shutting off the water supply. Such equipment includes, but is not limited to, a boiler or other heating system.

Note: Because you are working with a flame, often in a confined space, be aware of flammable materials near where you are working. In some cases, you may need to set up a non-flammable heat shield between the solder joint and flammable material nearby. Check with your local authority for applicable codes about the work you wish to perform and the necessity of permits before you begin your project.

Soldering copper pipes, also called sweating copper, is easy once you get the hang of it. The key is to recognize that you are heating the pipes, not the solder. The heated copper melts the solder. Follow the steps in this guide and you should be able to make watertight joints. It is recommended that you practice a few times on some spare parts until you feel confident.

  1. Remove all burrs from the inside and outside edges of the pipe with a deburring tool. Small burrs can result in variety of problems in the lifespan of the water supply system.
  2. Clean the outside of the pipe to a brilliant shine with a copper pipe cleaning brush, or simply use steel wool or emery cloth. If the copper is not clean, the solder may not bond properly and the joint may leak.
  3. Clean the inside of the female fitting in the same way as in step 1.

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