The Saturday Morning Home Repair Blog (SMHRB) is where we gather to discuss the many and varied aspects of home repair.  Some here are trained professionals.  Some, talented DIYers.  Some, hopeless thumb-hammerers.  All are welcome.  Please feel encouraged to ask questions, share successes, lament sags, drips and cracks and, as always, share any advice that you have for the rest of us.

Soldering is something most any homeowner can do. Today I will provide you with the basic knowledge to accomplish a solder joint that will out live you.

First, let’s talk some safety…
Safety glasses and gloves are a must for me, it is not much fun to get a drop of hot molten solder in your eye, trust me.

Fire extinguisher… well, duh, normally when soldering the water will be shut-off, not a good time to start a fire.

Spray bottle… when soldering near wood, especially old wood I spray the wood with water and allow it to soak in and spray again. If soldering against construction paper or something like plastic covered ducting, stick a piece of scrap sheetrock between it and the pipe. You can burn against a piece of sheetrock and it barely gets warm on the other side.

After cutting your pipe, it is always a good idea to ream your pipe. You just need to take the edge off and when you get to the end, just flick out the scrap. During the entire process, care should be taken not to get any debris or dirt in the pipe because it can cause problems later, like getting caught in the rubber washers or other delicate parts of valves.

Always clean the pipe with sand cloth (made for cleaning copper pipes and found at all hardware stores) until it’s shiny. If the fittings are new I might not bother cleaning them, but it’s not a bad idea to give yourself the best chance at a successful solder joint. I’ve never seen a leak caused by a pipe or fitting being too clean. Fittings can be cleaned with a fitting brush or sand cloth.

Flux is a paste used on the surface of the fitting and pipe being soldered and should be applied soon after cleaning to reduce oxidation.  Apply a thin coating to the pipe and fitting before assembling. When the flux is heated it will remove all remaining oxidation allowing the solder to adhere to the copper.  Do not use the fluxes mixed with solder, pre-tinning not needed. I use a non-aggressive flux such as Nokorode, the excessive flux is easily flushed out with water and does not continue to work on the pipe after soldering.

Now that the joint is fit-up and fluxed it is time to solder. But first remember these important rules: don’t burn yourself and don’t place yourself under the joint to be soldered unless you want hot flux and solder dripping on you. Pipe and torch tips will remain hot for a while after removing the heat.

Before I let you light up the torch, I’m going to tell you about solder and the basics of how it works. Many people will tell you that the heat draws the solder, but that’s not true. Capillary action is what makes it work, the physical attraction of the two materials and the closeness of the two surfaces just draws it right up. Of course the solder has to be in the right state or phase. The most important part of soldering is getting it there, after that nature takes over. Solder has three phases: solidest, pasty and liquidest. The pasty range is where we want to be; it has become liquid, but not watery. Different solders have different pasty ranges. While I was an apprentice, the move to lead-free solders started and there was a lot of fear because the only option at the time was 95-5 (95% tin-5% antimony) with a very narrow pasty range at a high temperature. It was much more difficult to use than 50-50 (50% lead-50% tin). The solder I use now is Silvabrite 100; lead-free, a wide pasty range for easier use and 0.4% silver which adheres well to copper. Can’t help but see it as analogous to where we are in our push to stop climate change, when needed humans came up with a solder; stronger, easier to use and safer. Progress…not as scary as some people think.

Almost ready to squeeze the striker, but first we should discuss what kind of torch and fuel to use. For most jobs I use a hand-held MAPP tank with a “Turbo” tip. Some torches come with an integral igniter, but the igniters are prone to failure and they lack the swivel tip that is easier to use in tight areas. Propane can be used in lieu of MAPP, it does not burn as hot but still provides more than enough heat. If I have large amounts of joints to solder I pull out the acetylene tank or “B” tank, not something most homeowners have or need. Oxy-Acetylene torches are not used for soft-solder joints, too hot.

Turn on the gas and hit the striker, flame on. The image on the right shows the nice blue cone of a well burning “Turbo” tip flame.  Unlike Acetylene torches, “Turbo” torches have one speed. To find the right speed after lighting it, turn up the fuel until the cone starts to distort then turn it down just enough to create a nice cone. If the fuel is set too low, the tip will heat up turning it red. If this happens don’t panic, just turn the fuel up and it will cool off.

Finally…lets get soldering. We learned above that heat does not draw the solder, what we want is a nice even heat. You want to use the area approximately 2 or 3 inches from the tip of the blue cone. Heat rises so always start on the bottom with the torch and solder. Always keep the torch moving, either back and forth while heating or drawing back the flame while feeding the solder. Warm the pipe first; then move to the fitting and check occasionally with the solder until it starts to melt into the joint. Draw back the torch and begin feeding the solder working from the bottom to the top on each side. Once full it will start dripping off. Remove all heat and feed a little more solder until it stops taking it. After it solidifies you can wipe with a moist rag to clean off excessive flux.

There are two common causes of leaks: if the leak is at the top of a joint, you likely overheated the joint causing the solder to become too liquid or burned out the flux. Turn off and drain the water. Brush some more flux into the joint and try again. The worst case is that you may need to remove the fitting and replace it with a new one. The other cause would be water, this you would realize while soldering when the solder won’t flow into the bottom part of the joint. You can try to boil the water out, move the flame about a foot down the pipe, get the hottest part of the flame on the pipe and slowly work back to the joint repeating until the solder flows. It’s always easier to make sure the water is completely off before ever cutting into the pipe. If you can’t get it to turn off, try to find a hose bib or faucet between your work and the shutoff valve. Another option is to shutoff the water at the meter and disconnect the union to allow for drainage.

Last couple tips: turn the water on slowly to avoid disturbing any sediment, after pressurizing the line remove the aerators from the faucets and flush out debris.

Originally posted to Saturday Morning Home Repair on Sat Jan 26, 2013 at 06:00 AM PST.

Also republished by J Town.

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