There’s a strong chance you’ve spotted copper pipe somewhere in your home, like around a hot water tank or under a sink. Copper is the metal of choice for potable water systems for a variety of reasons – the most important being that it is non-toxic and safe for drinking. The naturally occurring metal element is also preferred for various application types due to its high conductivity of electricity and heat, corrosion/fire resistance and durability.
The process of joining copper pipe and fitting is called soldering (or sweating), which is a critical step in the copper installation process. Solder is a metal or metallic alloy that historically consisted of lead (known as lead-based solder) and tin in various proportions. Today, due to the Safe Water Drinking Act and lead-free restrictions, solders that contain more than 0.2% lead are not permitted for use in potable water systems.
Solders that are safe to use on potable water systems contain a percentage of tin and a combination of other non-toxic metals. The melting point of solder is lower than copper, and when heated, solder melts and fuses the piping together once completely cooled.
Learning how to solder copper pipe can seem daunting at first, but by applying proper techniques and avoiding typical errors, it becomes much easier to execute a leak-free pipe joint. Let’s explore some of the most common mistakes professionals make during the soldering process.
In addition to choosing the proper type of solder for your application, you will need to select the right type of copper pipe and flux, a compound that promotes the flow of molten solder between the pipe and fitting through a process known as capillary action.
Flux is also formulated to remove any oxidation from pipe and actually etches pipe surface in preparation for the soldering process to be successful. Important variables, such as ambient temperature, local code guidelines and any jobsite time limitations, should all be considered prior to purchasing your soldering supplies.
Below, we’ve included some brief guidelines to keep in mind for your next soldering project.
Although petroleum-based fluxes are safe to use, they are required to be flushed with a chemical solution from the piping system due to their water insolubility. However, water-soluble fluxes become self-cleaning and flush away once water enters the system. Refer to manufacturer instructions for product-specific application and safety guidelines to ensure proper use.
Failure to properly prep both the pipe and fitting is arguably one of the most critical mistakes in the soldering process. To achieve a properly sealed joint, oxidation and oils on the copper surfaces must be removed using special cleaning tools. Otherwise, it is likely that the solder will not completely fill the cup of the fitting, resulting in a weak or leaky joint.
Each of the following steps should be completed as you prep copper pipe for the perfect joint:
1. After cutting the copper to the desired length, deburr (or ream) the inside of pipe end using a deburring tool to remove any small bumps or roughness (known as burrs) on the inside diameter or the pipe. If this step is overlooked, pipe pressure will decrease and water flow will be restricted. Any leftover burrs or copper shavings could cause noisy pipes when water enters the system.
2. Remove oils and dirt from the outside of pipe end and polish clean with an abrasive sand cloth, open mesh cloth, nylon grit pad or tube cleaning brush. For wet applications, a nylon grit pad or open mesh cloth are ideal due to their self-cleaning abilities.
3. Clean all openings of the fitting hub with a fitting brush.
It can be tempting to use a large glob of flux while soldering. However, we recommend evenly applying a thin layer of this product with an acid brush to copper pipe and the inside of a fitting – any excess flux should be removed prior to connecting them.
Applying too much flux will not only result in uselessly wasted product, but could also cause severe pipe damage over time. Once heat is applied to flux it turns to an acid; however, any excess flux will melt and travel through the inside of pipe, which may result in pitting and corrosion.
When heating the fitting to sweat the copper pipe, make sure you remove the flame as soon the solder melts. As solder melts, flux will pull the solder into the fitting cup. Too much heat will cause excess solder flow or flux to burn out, which will increase the chance of a leak path.
Pro Tip: Never heat solder directly because you risk melting and breaking it off completely. It’s best to heat the joint evenly and then position the tip of the flame to the bottom of the fitting hub. The solder will flow toward the heat source and ensure the joint is completely filled.
While the joint is still warm, immediately wipe away any leftover flux or solder drips with a dry rag to ensure copper pipe longevity. Excess flux may seem harmless; however, it can cause Verdigris, a greenish-blue discoloration commonly found on copper, bronze and brass, to form and destroy copper pipe over time. An old, rusting penny and the Statue of Liberty are great examples of Verdigris in action.
READY FOR YOUR NEXT SOLDERING PROJECT?
For a step-by-step guide on how to solder copper pipe, check out this video:
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