How To Solder

Many ambitious do-it-yourselfers shy away from soldering their copper plumbing connections, because of frustrating earlier attempts, fear of burning down their house, or someother negative connotation. Use the following steps to experience professional results.

You will need:

  • Roll of lead-free solder
  • Can of soldering paste
  • Flux brush
  • Sand paper
  • Propane torch
  • Cloth rag

Step 1

Putting the joint together.

After familiarizing yourself with the various fittings, you will find that there is always a male end of a connection (the pipe or a fitting where one side it is the size of the pipe) and a female end (the "hub" portion of a fitting that a piece of pipe fits into).

There will always be a male and female end being soldered together.

If this is not new construction, then you will have to drain the water out of the system, or at least from the general proximity of the area you are going to be assembling your new installation. If there is water close by, there will be steam present as you are heating your joint, which will make it almost impossible for you to make a water tight connection. The steam can blow the solder right out of the joint and make it very difficult to get the joint hot enough to get the solder to run.

Step 2

Prepping the joint.

Using plumber's tape or sand paper, "clean" the male end of your connection by applying the sandpaper to as much of the pipe or fitting as is going to fit into the hub female end. On 1/2" I.D. pipe, 1/2" of the pipe will slide into the female side, so clean off 3/4" of the end of the pipe making it look very shiny.

Next, using a wire fitting brush -- or for bigger fittings, a piece of sandpaper wrapped around your finger -- clean out the inside of the female end of the fitting, also making it look shiny.

Taking your flux brush, dabble it into the can of acid flux, then apply a coating to both of the shiny ends, the outside of the male end and the inside of the female end.

Step 3

Applying the solder.

Unwind about 12" to 16" of solder from the roll and make an "L" shape at the end of it so the leg of the L is 3" or so. Push your male and female ends together and then start applying heat from your torch to the hub of the fitting. The amount of time it will take for attaining the necessary temperature will vary, depending on the size of the pipe and the size of the nozzle on your torch, but 1/2" pipe will heat up in 10 to 15 seconds generally. After applying the heat to the joint for a few seconds, you can take your solder and start to touch the end of it to the joint at the opposite side that you are applying the heat to.

When setting the dial on your torch, adjust for a conical light blue flame within the larger blue flame. Apply the tip of the inner blue cone to the joint as this is the hottest point of the flame.

You want the whole joint get hot enough for the solder to run with complete coverage. And the coldest part of the joint will be away from the heat source, so when the solder starts to run there, it is hot enough.

Step 4

Wipe the joint.

When the solder liquifies, the flux will pull it into the fitting. You can visually inspect the solder as it runs around the fitting. Take a folded-over or bunched-up rag and wipe around the joint to complete the process.

If you are doing several joints that are in close proximity to one another, the joints will stay hot enough for you to wipe several at a time in one step instead of wiping one, then soldering and wiping the next.

Step 5

Test for leaks.

You can cap off all your stubouts in new construction and apply an adaptor from an air compressor with a gauge to test your system for leaks, or turn on the water and pressurize for a leak test in a remodel.

Step 6


  • Using a cap, goggles, and gloves is recommended, but when working overhead you should also wear a long-sleeved shirt. You can get burned from the heated flux dripping down onto unprotected skin before you even start applying solder.
  • Many times during a remodel, opening the outside sillcocks and lifting lever open on the temperature and pressure relief valve (T - P valve) located on the water heater will help drain a system that seems to drip, drip, drip at the joint you are trying to solder.
  • If you have a problem joint that has a pin hole leak and you are having problems with water in the lines, it sometimes can be fixed by focusing the torch right on the pin hole, getting just some of the solder in that area softened up, then painting the area with flux and repeating with more heat and flux as necessary. You must be able to see the solder run for there to be a solid joint.
  • You will usually run into a few joints that will be close to wood and there are a few things you can do to avoid a fire:
    • Pre-assemble and solder a joint somewhere else safe, then dunk it in water so you can touch it and slide into the area that was near the combustible material.
    • Learn how to aim your torch so it blows in a direction away from the wood, yet still catches some portion of the joint. Professionals use a large propane tank (6 to 15 pounds) with a long hose attached and a torch tip at the end of the hose which gives it much better maneuverability for close quarters work than the smaller propane bottles where the tip screws to the top of it making it over a foot long.
    • Heat the pipe first, away from the joint and wood a few inches away, then go right to the joint after a good 15 seconds. Then start applying the flame as close to the joint as possible to get the solder to run, while aiming away from the wood as much as possible. Have a squirt water bottle handy to wet down any suspect areas of wood that have gotten charred or caught on fire.
    • In some very difficult situations, the pros will use a ceramic cloth that can be slid between the pipe and wood framing.


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