Rubber Seat Washers in Shutoff Valve

[jacksmith7]

When our house was built, the plumber installed 3/4" copper runs to the bathroom rough-in in the basement. At the end of each run, he put a shutoff valve with rubber seat washers; the valves also have the small drain cock on the side containing a rubber seal.

When I sweat the outlet pipe to these valves, can I do it with the water on and the valves closed, or will the heat melt the rubber washers?

 

[Krow]

You can solder as is without shutting off the water, but do not overheat. Remove the bleeder or small drain cock before soldering