Skip to main content

Apply Flux and Assemble — Apply Flux

Beginner4 hours

Part of project

How to Solder Copper Pipes for a Permanent, Watertight Joint · Step 4 of 9

Helpful?

In this video

Using a flux brush, apply a thin, even layer of soldering flux to the cleaned outer surface of the pipe ends. Also, apply flux to the cleaned inner surface of the fitting. Immediately insert the pipes into the fitting and give them a slight twist to ensure even coverage. Wipe away any excess flux from the outside of the joint.

Goal: Prepare the joint for soldering

Used in this video

  • Flux BrushApplying an even coat of flux to the copper surfaces.
72.7K views1.5K2 minutes
Home Repair Tutor

644K subscribers

View Channel

FAQs

What are the most critical safety precautions I need to take when soldering copper pipes?

Always wear appropriate eye protection and heavy-duty gloves. Ensure you have a fire extinguisher or a bucket of water nearby, and work in a well-ventilated area to avoid inhaling fumes from flux and solder. Never point the torch flame at yourself or others, and allow joints to cool completely before touching.

This project is listed as 'beginner' difficulty, but soldering seems intimidating. What makes it beginner-friendly, and what's the hardest part?

While it requires precision and a steady hand, the basic steps are straightforward and repeatable, making it accessible for beginners. The most challenging aspect is often achieving the right heat balance – not too much to burn the flux, and not too little to prevent the solder from flowing properly. Practice on scrap pieces first to get the feel.

What are the most common mistakes beginners make when soldering copper pipes, and how can I avoid them?

A common mistake is insufficient cleaning and deburring, which prevents solder from adhering correctly. Another is overheating the joint, burning off the flux before the solder can flow, leading to a weak or leaky connection. Ensure surfaces are spotless and heat evenly, focusing the flame on the fitting, not directly on the pipe, until the solder is drawn into the joint.

The tool list includes both propane and MAPP torches. Which one should I use for soldering copper pipes, and why?

Propane torches are generally sufficient for smaller diameter pipes (up to 3/4 inch) and offer good control for beginners. MAPP gas burns hotter and is more efficient for larger diameter pipes or if you need to work faster, as it heats the joint more quickly. For most DIY home plumbing repairs, propane is a good starting point.

Apply Flux and Assemble — How to Solder Copper Pipes for a Permanent, Watertight Joint (Step 4, Video 2) | Stesso