Hi: i was trying to install a new ball valve on my incoming cold water line. I drained the line, sandpapered the copper pipe & inside of valve fitting, applied flux etc.. But when I went to heat the joint with my gas torch to apply solder, the joint simply would not heat up enough to get the solder to melt and go into the joint. I am using the standard plumbing torches available for DIYs at home depot. I have the feeling the heat is simply being dissipated away in the copper pipe so the joint never heats up enough. Is there any trick I can use, or is it possible to buy a hotter propane torch etc.. I am sure plumbers solder stuff onto existing lines. what is the trick to getting the joint hot enough? thanks.
Water in the pipe will cause this problem. Try putting a wad of white bread into the pipe to hold back the drops temporarily....good luck.