Can this be done? I can't find any of the galvanized "dresser" coupling and would have to order. I think I have seen folks use the PVC on galvanized before. Just wondering if this is common. Thanks in advance.

Generally no it cannot be done

The zinc will react with the PVC and the compression seal (even has a name - galvanic corrosion) and eat away the pipes

Galvanized is not perfectly smooth like PVC, so the compression gasket cant guarantee a flat enough joint

PVC and galvanized will react to weather differently. The expanding, contracting, and shifting will make the joint brittle

Local codes restrict where and how PVC compression fittings can be used even on other PVC pipe

I'd recommend a dielectric union (best) or a galvanized-to-PVC threaded adaptor if you have to transition from one to the other

Thanks. I am dealing with a 70 year old galvanized 3/4" water line from the meter to the house. I am really scared to even cut into it because of the shape it is probably in. Can you thread something like that? I was just thinking the compression couplings would be a good low-risk solution.

The existing pipe is likely in sections. Dig up one section, detach union (or cut pipe), unscrew both ends, replace with new galvanized pipe screwed into place with tape and union.

Thanks. Yes, that is a good plan. I didn't think about that. I am having pressure loss issues in the existing galvanized pipe. So, I am considering placing a "T" at the water meter and running copper or PVC back to the front of the house and coming up into an existing faucet connection, leaving the old galvanized pipe in place. Basically having a parallel feed.

Normally, I would just replace the old pipe. However, I don't know where it comes up into the house. It must be coming through the slab. So, I figure I will never be able to get the old one fully replaced and even a 1' section through the slab will still choke my flow.

I figure this is a better situation for a "cutover" as well. I can just get the "T" in place with a ball valve one day and then tie into the faucet another.