My bathtub faucets (Ganze) are leaking so I took them apart and see that they are all plastic inside - valve cylinders, etc.. I would insert a picture here if I knew how, or if it's even possible. Anyway, I want to replace all the plastic parts with standard brass fittings. On the other side of the wall (which I gladly have access to, the hot and cold water feed into a brass fitting about 9 inches long with cold on one end hot on the other and a shower connection on top and the regular faucet connection on the bottom. Will I need to replace this part too if I want to replace the valve cylinders, etc..? Thanks kindly to anyone who can help.