"Stretch" wrote in message
oups.com...
If you replace the entire piping system with copper, the galvanic
action problem should not rear its head. If just replacing parts, it
could be a problem. If you replace black pipe with plastic, you can
use CPVC or PEX on hot or cold lines. Do not use PVC on in house piping
per International Residential Building Code P2904.5. PVC is allowed
for the service line from the street to the house. Note: Codes in your
area may vary, consult your local building inspector.

Stretch

There is no problem transitioning from Galv to copper if you use a
dielectric coupling which can also serve as a union (which is usually also
needed) when joining the threaded pipes back together.