What challenges do I face if my existing plumbing is Type M? Existing copper is 35+ years old.

I purchased Type L copper lines. I don't think my fittings were typed.

Hey Alpac:

No problem on fittings. They are universal fit/type.

Pipes are different thickness...

TYPE M... Heat
TYPE L... Water
TYPE K... underground water.

You have type M in your home for water... a lot of homes built in the 70s have type M for water... not a really bad thing... just thinner, may break down sooner then the type L.. but all in all... I see it quite a bit!

So, anyway, fit up pipe/fittings as usual... just be careful not to overheat the type M... and solder as usual for type L pipe.

Good luck... Mark