The supply pipes in your walls are designed to last a long time, so they only need replacement every 70 to 100 years, depending on the materials used. Drain lines made of cast iron last a similar length of time, while PVC drain pipes may last 25 to 40 years. Appliances and fixtures, such as toilets, water heaters, and faucets, have varying lifespans depending on the materials they’re made of and the typical usage patterns of your household.