After taking the downspout off of my 50 year old tub, I found the brass threaded pipe was corroded. I got a new downspout and new threaded brass pipe, but when I taped it and screwed it into the existing female connection it began to leak. There looks to be a bit of the old pipe in the threads of the female fitting, but other than that it seems to be ok.

My question is, rather than replacing the female connection, can I solder the threaded brass fittings together, or will the solder not run properly into the fittings?