Over time, galvanized pipes fill up with calcium and minerals, and there is no code-approved way to clear the line. Calcium and minerals are leeched out of the water and bond to the inside of galvanized pipe, it forms a rock-like substance. These minerals begin to choke off the inside of the pipe and slow the water down. As water slows down, more calcium is removed from the water. Eventually the inside diameter is reduced so much that water does not flow freely. The best solution to this drain problem is to replace the line with High Density Polyethylene (HDPE) pipe, which will provide better pressure and will not accumulate calcium and minerals.