couple of tips. when you don't want to mess up a near by joint you wrap a wet rag around it. you can buy a cloth fireproof shield (inexpensive)that you can tape to the wall so as not to burn it.if you're getting a small trickle of water and you can't get the solder to flow then you pack the inside of the pipe with bread.and sure you can replace the washer and packing.ps when you solder on a new shutoff valve it's best to dissasemble it so you don't burn the rubber washers up.same thing goes for your dielectric unions.