January 20, 2011 at 10:34 PM by Dr. Drang
I spent much of Tuesday down in my basement, taking out an old water softener and putting in a new one. Most of the time was spent
- measuring lengths of pipe;
- remeasuring lengths of pipe;
- cutting pipe;
- soldering pipe;
- waiting for recently soldered pipe to cool down so I could do more measuring, cutting, and soldering; and
- waiting for someone else to come home to hold the pipe while I soldered it in place.
Softener installation suffered delays due to genetic defect (only 2 hands). Possessor of required 3rd hand now having after-school snack.
One thing I wasn’t planning on—and the reason I had to do more measuring and remeasuring than I expected—was the need to reroute the inlet and outlet pipes. I’d’ve thought the water softener people would have standardized on the positions of these pipes to make replacements easier, but apparently they’ve decided that innovation in water softener technology requires the freedom to put the pipes wherever they damned well please. My old water softener had its inlet on the left and outlet on the right. The new one has the inlet and outlet reversed, so I had to cross one over to the other side.
Which looks kind of goofy, I’ll grant you, but it was the only way to get things to line up. And since we seldom entertain down in the furnace room, I’ll probably never have to explain the crossover to guests.
Tallying up all the elbows, sleeves, and adapters, I made ten solder joints, and I couldn’t test any of them until the last one was finished and the new softener hooked up. To my great amazement, not a single one of them leaked.1 This would, no doubt, surprise Mr. Meyer, my junior high metal shop teacher.
(Overall, I was pretty good in metal shop, but my soldering was just awful. I still have the funnel I made as one of the class projects, and its solder joint is a globby mess. Many retries before it was finally water-tight.)
The trick to making a solder joint is to get both parts of the connection good and hot before touching the solder wire to it—something I never had the patience to do in junior high. It’s actually fun to watch a good connection being made; the solder melts instantly and is quickly drawn into the joint by capillary action.
Done right, the solder will even defy gravity. Although I made many joints with the pipes held in a vise at my workbench, the lower elbow joint on the left side of the photo had to be made with the pipes in situ. On this joint, I made extra-sure the pipe and elbow were hot enough, and when I put the tip of the wire to it the solder went right up the pipe into the annular space between it and the elbow. (The drips you see are from excess solder that ran down after the joint was closed.)
The Metals Handbook Desk Edition from ASM International defines soldering, brazing, and welding like this:
Soldering: A group of processes that join metals by heating them to a suitable temperature below the solidus of the base metals and applying a filler metal having a liquidus not exceeding 450°C (840°F). Molten filler metal is distributed between the closely fitted surfaces of the joint by capillary action.
Brazing: A group of welding processes that join solid materials together by heating them to a suitable temperature and using a filler metal having a liquidus above 450°C (840°F) and below the solidus of the base materials. The filler metal is distributed between the closely fitted surfaces of the joint by capillary attraction.
Welding: (1) Joining two or pieces of material by applying heat or pressure, or both, with or without filler material, to produce a localized union through fusion or recrystallization across the interface. The thickness of the filler material is much greater than the capillary dimensions encountered in brazing. (2) May also be extended to brazing and soldering.
Most metallurgists I know don’t use welding as the catchall term suggested by definition (2), reserving it for joints in which the base metal is actually melted. Soldering and brazing are processes in which the base metal doesn’t melt—the difference between the two is a somewhat arbitrary temperature boundary associated with the melting temperature of the filler metal.
Alloys typically melt over a range of temperature, and the terms liquidus and solidus refer to the upper and lower bounds of this range. When the alloy is between the liquidus and solidus, it’s a liquid/solid mush or slurry. In some alloys the liquidus and solidus are the same; these are called eutectic alloys. Eutectic (or near-eutectic) alloys are common in solders, because solders need to be fully liquid to get drawn into the joint and it’s best if they liquify instantly instead of going through a mushy phase.
Although I haven’t linked to them, Wikipedia’s articles on soldering, brazing, and eutectic compositions are pretty good. Worth reading if you don’t have a copy of the Metals Handbook Desk Edition handy. (Oh, I’m gonna make tons of money off that affiliate link.)
One of the threaded joints did leak a bit, but that was easily fixed with a little pipe dope. ↩︎