Without a doubt soldering can be one of the most exasperating tasks in the plumbing trade, but with a bit of training and practice it becomes second nature.
Properly cleaning the pipe and fittings is critical. Do not make the common mistake of thinking a piece of pipe or a fitting is new, therefore it doesn't require cleaning. When raw copper is exposed to air it oxidixes very rapidly. In fact, if it has been more than two hours since you cleaned the fittings, it would be best to clean them again.
The best method of cleaning the exterior wall of pipe or fittings is to use "Plumbers Emery cloth". You can find precut rolls of plumbers emery which are 2" wide by 10' or 50'. While the common cloth backed plumbers emery will work ok you will find that for a couple dollars more you can get the open weave "Screen type Plumbers roll" which will outlast regular cloth backing by about 5 to 1.
To clean the inside of female fittings use a stainless steel ID brush sized for the size of pipe or fittings you are using. You will often see the deluxe models in the big box stores that have a nice plastic handle set into the wire frame. They work fine, but for about 1/3 the cost you can get the inexpensive open wire frame handle type which will work just as well.
Some people like the 4 in 1 type brush which has both ID and OD brushes for 1/2 and 3/4" copper in one handy tool. In practice you will soon find that the 1/2" OD brush is worn out long before the others and often you will find yourself working in a tight spot where you simply do not have clearance for the all in one type brush. In my humble opinion you would be better served to buy the inexpensive individual brushes and keep a spare handy for the 1/2" size. When i have a lot of fittings to clean I often cut the loop of the end of a handle, then chuch the handle shaft into my cordless drill and use the drill motor to spin the brush to quickly clean the fittings.
Absolutely do not touch the cleaned portion of a fitting with your finger tips, as the oil in your skin will get on the surface and make soldering difficult.
Apply flux with a disposable acid brush. Acid brushes are often sold loose in the hardware stores for about $.10 each. Keep a couple spares handy so if you happen to drop the brush and contaminate it, you have another one handy.
Personally I prefer to use petroleum base flux, but many local codes now require that you use the water base type. Water base flux requires a bit more soldering skill to get the feel of it.
Apply the flux on the male end of the pipe with an acid brush only. Do not brush flux inside the female fitting. (Do not apply flux with your finger tip)
Fit all the pipes into the fitting before heating, and check the fit to insure there is no unnecessary stress on the pipe which might hold the fitting out of alignment while soldering. When possible, after a fitting is put on the pipe, rotate the pipe or fitting a bit to insure the flux is evenly distributed.
When soldering a valve you may elect to remove the stem or you can make sure the valve is open and wrap a wet rag around the body of the stem to absorb excess heat, leaving the solder joints open.
The type of torch you use will have a great effect on how well you can solder.
When looking at torches in the hardware store you will see the all in one "plumbers pencil flame" toch kits, which have a pencil flame torch head, propane cylander, spark igniter, solder, flux and brush all packaged in a neat little metal carrying case.
Pencil flame type torches have many drawbacks. If you examine the torch tip you will see the combustion air inlet ports are right at the base of the burner tip. That only allows about 1/2" travel for the fuel and air to mix and the end result is a much cooler flame. That means it will require a lot more preheat time to get a joint hot enough to properly solder. Those type of torches also require that the torch tip be held above the fuel tank at all times. The require two hands to light the torch and being a constant flame torch you have to be very careful when setting it aside for a moment to prevent creating a fire hazard.
I personally prefer the instant on turbo torch design such as a BernzOmatic TS4000. If you examine the turbo torch designs you will note that the combustion air intake ports are at the base of the tube to the tip. Inside the tube there is a spiral piece of metal that causes the fuel and air to swirl as it travels through the tube. That insures a much better fuel air mixture and a hotter flame. The instant on type have a trigger button. When the trigger is pulled the gas valve opens and a built in igniter lites the torch for a total one handed operation, and when the trigger is released the flame goes out intantly so you do not have a fire hazard when setting it down quickly. Perhaps the greatest advantage is that these type of torches are an all position torch, which means you can hold it completely upside down if necessary, therefore you have a full control over where you point the flame. While an instant on type torch will cost about $30 you will quickly recover your cost in fuel savings, by example, when using a constant flame type torch I typically use about 3 to 4 tanks of propane to plumb a 3BR 2 Ba house whereas with the instant on, instant off type I can typically complete the same size job with one tank of fuel.
A word of caution. Most of the turbo torches will also burn MAPP gas. The preferred fuel for residential plumbing is PROPANE. MAPP gas produces a much hotter flame and great care must be taken to prevent annealing the copper which would then make soldering nearly impossible.
The advantage of having the MAPP gas option is for when soldering larger diameter pipes outdoors in the wind, or when running copper under a slab where we are required to use wrought copper fittings and Braze the joints.
Pull about 10" of solder off the roll and bend the end into a J hook.
Apply heat to the underside of the fitting, with the tip of the flame directed toward the pipe. Allow a few seconds to preheat, then test the heat by touching the tip of the solder to the joint on the opposite side from were you applied the heat. If the solder begings to flow, continue feeding solder and pull the flame back away from the pipe. The solder should quickly flow all the way around the joint and for a small bead on the underside of the pipe.
Quiclky wipe the joint with a wet rag to remove all excess solder and flux.
If the heat was correct the solder should be brite and shiny with just a thin film of solder on the pipe.
Allow the joint to cool a few moments then thorougly wipe all exess flux off the joint. (Flux is an acid, and if excess flux is left on the joint it will cause premature corrosion on the fitting and joint.
