Apparently modern housing uses PEX water pipes, but my house has a mix of PEX, iron, and copper pipes. The water flows just fine. I'll probably rip out the iron

Apparently modern housing uses PEX water pipes, but my house has a mix of PEX, iron, and copper pipes. The water flows just fine. I'll probably rip out the iron and copper eventually when I do a major remodel, but I'm not stressing about it.