best way to seal off an open water pipe?
You can either put a valve there and shut it off, or just solder an end cap to the pipe. They're made for every size of copper tubing. Yours is probably 1/2 inch.
get a blowtorch, a end cap, soldering flux and soldering wire. you start by adding the flux to the end of the open pipe, put the end cap on and over the end of the pipe and heat the end cap and the connecting point a little, a couple of seconds at most, then touch the wire on and around the whole connection with the blow torch on low and running at the connection point and the solder should melt and be sucked into the connection crack by back pressure and by the flux, and your done, test the seal so you know it won't leak at all and if it does, pull the end cap off and try again when the pipe is dry.
