If you’re used to handling home plumbing projects, then you’ve probably heard about a product known as flux. Flux is one of the most commonly used products in plumbing.

Flux is applied in pipe connections that are joined together by soldering. The process of connecting two joints by soldering is often referred to as sweating metallic pipes together.

Flux is part of an effective soldering process. Thus, flux is extremely important in sweating. By learning more about this product and understanding how it works, you’ll be better placed to connect copper fittings properly.

plumbing flux


What is Flux?

Flux comes as an acid-based paste and is soluble in water. Thus, it’s easy to clean it up by simply using a piece of cotton rag and water to wipe it off. To use flux, you’ll apply it to the copper fittings that you’d want to join together.

The paste works by drawing in the soldering material once it’s heated with a soldering torch. The acidic component making up the flux works by attracting the solder material into the joint created between the copper fittings being joined together.

As the solder is being drawn deeper into the joint, it fills the entire gap, thereby creating a tight bond.


Preparing the Copper Fittings for Flux

There are certain things you need to do before applying flux. You need to prepare the copper fittings beforehand for the best results. First, you need to ensure that the copper fittings you’re connecting are extremely clean.

It’s necessary for them to be clean before sweating them with the solder and flux compound. Start with cleaning the pipe surface around the end section you want to solder. Use sandpaper (fine-grip type) to clean the pipe until it’s shiny and bright.

Next, take a wire brush (copper-based) and use it to clean the interior area where the fitting will be soldered into. Also, sand the edge of the pipe to remove any roughness.

Cleaning the pipe and removing any roughness will create a better surface for the flux to bond.


Applying Flux

You’ll need to use a special brush to apply flux. You can find the flux brush from your local hardware store. Once you get the brush, dip it in the flux compound.

Both sides of the brush should be well coated with flux. Next, use the brush to apply flux around the shiny copper surface. Also, apply flux around the inner surface of the fitting.

Flux should be applied around the entire surface you’ll be soldering. However, be cautious when applying flux to avoid it from spilling to pipe surfaces you won’t solder since the solder travels to wherever flux is applied.


Making the Connection

Once you’ve applied flux on the exterior surface of the pipe and the interior of the fitting, press the two pieces together. Next, take a soldering torch and use it to heat the pipe connection.

Heat the fitting for around 30 seconds. Then press the soldering reel onto the connection. Doing so will allow flux to pull the solder toward the fitting. Once you notice solder bubbles forming from the seam, then you’ll know that the pipe connection is ready.


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