I'm in a bit of a fix. I removed one brass fitting from a tub cold supply line that was in 1/2" female iron pipe (fip) in the floor of a bathroom on a concrete slab. That one took some torque, but came out just fine and I attached a nipple for a shut off valve to the 1/2" fip in the floor, however, the 2nd brass fitting was completely rusted into the hot water supply line. I tried deep penetrating sprays. I tried heat. But now the brass fitting is completely broken off flush in the supply line. I tried a nipple extractor to see if I could get it to turn from the inside, but it's not budging. Since this is a supply line coming out of a concrete slab, my options are limited. I'm wondering if I can have a 1/2" fip thread nut welded onto the mouth of the supply line so I have something to fasten the nipple to. What do you all think - is that a viable option? Any other ideas?