Things You'll Need
Acid core solder
Brazing torch (propane etc.)
Respirator and eye protection
Brazing galvanized pipe can be easily if the correct steps are followed. Steel is often galvanized by dipping it into a zinc solution. This process protects the surfaces of the steel from rust. When heated or burned for the purposes of brazing, poisonous and potentially lethal fumes are created. It is essential that the galvanized coating is removed prior to brazing. This must be done in a well ventilated area. Once removed, brazing your pipe is a simple matter.
Put on your respirator and eye protection.
Remove the dull grey galvanized layer of coating from the steel pipe around the site you plan to braze. Use your angle grinder to gently remove this layer, exposing a shiny, bright layer of steel under it. Be careful not to remove too much steel, as the galvanized layer will be quite thin, and you do not want to reduce the integrity of the pipe. Use your wire brush to access any areas difficult to get to with your grinder.
Turn a fan on pointing at you from behind. This will help to move any fumes away from you created by any residual galvanized coating. Do any galvanized brazing outdoors when possible.
Light your torch and begin heating the surfaces of the pipe you plan to join.
Apply a layer of flux over the site you wish to braze. Flux prevents the steel and the solder from oxidizing.
Touch the tip of your solder to the site you wish to braze. When the correct temperature has been reached, the solder will melt and fill the gap between two adjoining pipes. Start at the top and work down, ensuring the entire gap is sealed. Clean the site afterward and then test for leaks. If leaks are found, thoroughly clean the site with your wire brush and heat and apply flux and solder again.
The cleaner the surfaces of the metal, the easier the application of solder will be.
Always wear eye protection when working with metal, and work in a well ventilated area when working with galvanized steel.