re: Replacing galvanized water pipe under house on piers

i'm in the pex camp. the first time i used it, my brother and i replaced all of the water lines in my rental (kitchen, 2 baths, laundry room and two outdoor faucets) in about 2 hours. no open flame like sweating copper and no glue drying time like pvc.

your bigger problem will be getting the old line out. after 74 years, the galvanized pipe will not simply unscrew from the fitting. the weakest point is apparently right at the fitting, and the pipe will twist off, always on the wrong side of the fitting.

i had a water main rust through on my 1945 capital heights house, and coburn supply suggested a fix for me that has worked well. cut the bad pipe off 6 inches from each end. use a compression fitting and a 6" nipple to restore threads to each end, then screw on a transition piece for whatever new material you use (pex, pvc, etc.)

each end would have a combination of this
compression fitting
galvanized nipple
transition from iron pipe to pex

attached by compression fitting to the remaining 6" of the cut-off pipe. your connection on each end would then be old pipe-compression fitting-iron pipe nipple-transition from iron pipe to new material.

you can make up both of the connections on the workbench, then all you have to do under the house is cut the pipe, attach the connections to the cut-off pipe and run the new material. while you're under there, you can T off the new material and add a new run for an outdoor faucet.