galvanized repipe to PEX

So my house has very old galvanized water pipe. Had to turn off water a year ago and when It was turned back on I had no cold water in the bathroom. the sludge in the pipe was held back due to the water force. needless to say I had to replace some pipe. the size of the hole that of the feed pipe was ¼ or less due to build up. I used PEX and push on connectors to install a new water heater yesterday (relocation) . was so easy with pex. so I want to replace the old galvanized as far back as I can get hopefully to the water main. Would ¾ PEX be okay? I know it’s ID is smaller than copper and that what the charts go off of. Here is what I had in mind: *note if I can’t get all the way to the water main can I cut the galvanized and use a compression fitting or something to go to PEX. *note would the threads of the galvanized pipe still be good after all this years?

If you use a manifold the way you indicate, then 3/4" PEX will be adequate. You will have a hard, if not impossible, time finding a compression fitting which will fit PEX AND galvanized steel pipe. The threads will still be good if they have not rusted through from the inside.

I was thinking shark bite if that would work. if not i could do galvanized to a copper stub or galvanized to threaded galvanized stub. that is if i can use a compression fitting on galvanized. sure its half a$$ but that pipe in the house has to go, its bad real bad.

If you have threads left on the galvanized, I'd consider a coupler to allow you to connect to the pex. I don't think the OD of galvanized would be compatible with a Sharkbite using a compression fitting. they do make an adapter specifically for this http://www.cashacme.com/prod_sharkbite_pushfit.php to go from the threaded galvanized to a push on pex.

You can cut the galvanized and put a dresser coupling on it. Come out the other side of the dresser with a galvanized nipple and put a pex female adapter on and your ready to go to pex. Shark bites do not fit galvanized pipe. If the threads on the galvanized has been under ground for long I wouldn't trust it to tie on to.