My mothers house is around 50 yrs old and has the original cast iron plumbing in it. In one of the bathrooms the bathrooms there is a tub/shower combo. there has been new faucets and new shower head installed and the water at the tub part works great. however, there is no water comming from the shower head except a trickle or drip through the head. I dont know for sure but im guessing the older pipie has blockage from rust possibly. my question is ... could that piece of pipe goining to the shower head be replaced with pvc or pex or what would you recomend. thanks