: NIBCO in their instructions says to solder with the valve CLOSED to protect the seats. Yes, all ball valves have some type of seat. This said, it is then imperative to have the system open somehow on both ends to avoid pressure build up. SO we often solder carefully with the valve open.
: NIBCO also points out that lead-free solder melts at about 460 and teflon seats are damaged at 500. SO this job needs to be done quickly with some skill. Prolonged heating of the valve is a disaster.
Thanks for all the replys. I will quickly solder it with the valve open and free of any water. Thanks