How to Apply Flux to Copper Pipes

Flux is the substance used that allows solder to distribute evenly when working with copper pipes. Applied correctly, flux cleans copper pipes to create an optimal environment for successful soldering. Learn how to apply flux to copper pipes to achieve the best results.

Difficulty: Moderate

Instructions

1. Consider the two types of flux to use when you work with copper pipes. Tinning flux contains solder bits; pasting flux has no solder added to it but is water-soluble for easy cleaning. Realize that additional solder is necessary when you work with copper pipes that supersedes the amount contained within tinning flux.

2. Choose a rosin-based flux that works well to solder copper pipes. The alternative to a rosin flux is an acid flux which is used to solder heavier metals (and is not to be used on copper pipes.)

3. Ensure that the copper pipes to be soldered are clean. Open the flux paste container and mix up the flux using the flux brush. Mix until the flux is gray in color. Use the small brush that comes with the flux paste to apply a thick coat of flux on all clean surfaces of the copper pipes--the outside of the pipes and on the fittings inside of the pipe. When the copper pipes are fitted in the correct position, twist the pipes slightly to allow the flux to evenly coat the copper pipes before you solder.

4. Dry fit the flux-covered copper pipes before you solder to ensure a proper fit.

Tips & Warnings

• Clean the flux brush before and after you apply flux to copper pipes as unwanted debris can have a negative effect on the soldering process.
• Wear protective gear before you attempt to solder copper pipes to ensure your safety during the soldering process.