Mikepier wrote:

Was at Lowes tonight picking up stuff for hooking up my HW heater
this weekend and found out they did not have anymore 1/2" Tee's
in black iron for my gas line. But they had galvanized 1/2" Tee's.
Can I mix the 2?

I had to hook up a small electric water heater a few years ago and used
a combination of short-length galvinized and regular steel pipes and
tees near the tank, and used PEX feed lines to and from the tank.

In about 3 years the non-galvinized sections were very rust on the
outside, and really badly crudded-up on the inside, creating rusty water
if the hot water wasn't used for a few days (this is a small tank -
about 3 or 4 gallons). There was even some leaking of these pipes too.

I replaced everything with galvinized and no rust and no leaks for about
2-3 years now.

For a gas line, there is some water in natural gas - you're supposed to
put in a drop-trap line to catch the water before runs into your
appliance so the water can accumulate there. I'd be using galvinized
for that if it were me.