But when you own your own house, the renovations go toward your equity in the house. All your rent does is go into the landlord's pocket.

You're probably going to have to replace at least some pipes. With the cost of copper at the moment it's guaranteed to be damned expensive, but it's worth it. Most codes in the northeast don't allow PVC for supply lines due to bursting issuesin cold weather, but will allow Cpvc (PVC lined copper). The problem with Cpvc is that you have to re-plumb whole areas of the house with it as opposed to merely fixing the problem areas.