Category Archives: Sweat Fittings

Sweating occurs when the water inside a pipe is much colder than the surrounding humid air. When warm, humid air reaches cold pipes, drops of moisture form and drip as if there was a small hole in the pipe. One effective way to control the moisture problem of a sweating pipe is to insulate it by using self-adhesive thick “drip” tape. Deelat Industrial offers superb pipe wrapping tape which features a thin premium grade plasticized PVC film coating. It has excellent resistance to weather, moisture, and corrosion.

Copper Pipe Sweat Fittings: Applications and How to Solder Copper Pipe

Copper piping is widely used in plumbing applications. One common way for creating water-tight seals in your piping is by sweating – or soldering – the copper piping. This is a process of attaching a fitting, or pipe joint, to a piece of copper piping. Copper fittings come in a variety of shapes to help in routing plumbing pipes, including T-joints, L-joints and curved joints.

Sweat Fitting
Sweat Fitting

Fortunately, copper pipe sweating is straightforward, and it’s possible for beginning DIYers to accomplish. The process can be accomplished with basic tools, like pipe cutters, a wire brush, flux paste (which is sometimes called solder paste), a butane torch, and lead-free solder. Once you’ve selected the correct pipe fitting – both in size and shape – you can begin sweating the fitting to create a long-lasting, waterproof joint.

How to Properly Sweat a Copper Pipe Joint

Copper pipe soldering begins with some prep work, including preparing the pipe and fitting for the solder. First, you should measure the pipe, and be sure to include the added length of the fitting that will be attached. In general, one half-inch should be added to the length for each fitting that will be used. Then, the process is fairly straightforward. Steps include:

  • Cutting the pipe: Start by cutting the pipe to size. Pipe cutters are specialized tools for this process, yet a hack saw will also work. Remember that the length of the pipe will grow roughly a half inch for each fitting that is attached, so don’t over- or undercut the pipe.
  • Removing the burrs: When you cut the pipe, burrs will form on the end, and these must be removed. If they’re left behind, they can diminish the integrity of the solder. You can accomplish this task by using a wire brush inside and outside of the pipe.
  • Cleaning the pipe and fitting: Next, clean the pipe and fitting using a specialized pipe cleaning brush, sandpaper or steel wool. This will prepare both the fitting and the pipe for soldering, and it’s an important step, as debris and dirt may have collected on either end, which can weaken the bond.
  • Apply flux paste to fitting and pipe: Solder or flux paste is a bonding solution that helps maximize the strength of the joint. It should be spread evenly around the end of the pipe on the outside, as well as on the inside of the clean fitting. Then, after the fitting has been cleaned and covered in flux paste, you can attach the pipe.

    Sweating a copper pipe fitting
    Sweating a copper pipe fitting
  • Sweat the joint with your butane torch: Finally, once the fitting and pipe have been connected, it’s time to heat the joint. If you’ve never used a butane torch, there is an outer flame (darker blue) and inner flame (lighter blue). The inner flame is much hotter, and should be applied directly to the fitting. Next, run the flame along the middle of the pipe, and be sure not to heat the areas where flux paste was applied directly. Don’t overheat the copper pipe either – this will result in discoloration.
  • Apply solder to the joint: The last step is to apply lead-free solder to the joint. Solder is a metallic substance that melts easily. When the pipe has reached temperature, solder will melt easily along the joint. To create the seal, apply a light coat of solder around the joint. But be sure not to over-apply. Adding too much solder can cause leaking, allowing solder to seep into the joint, which can diminish the effectiveness of the pipe.

    Copper Pipe using Sweat fittings
    Copper Pipe using Sweat fittings

There you have it. Sweating a copper pipe is as easy as that. Of course, be careful once you’ve soldered the pipe; it will be very hot. Therefore, you need to allow enough time for the pipe to cool. Once it’s cooled, you can finish the solder by cleaning off excess solder with a shop rag. Then, you’ll have a properly soldered joint that will last for a decade or more.

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