Our house is almost 100 years old. Hot water heat, with pipes outside the walls in two rooms( they go from floor to ceiling). Knocking noise coming from bathroom area randomly, ( in the floor? walls? I can't tell for sure) not only when water has been used. Water can be heard dripping down the heat pipe that is in the living room below the bathroom. Also, trickling noise heard from toilet. Started with three knocks occasionally, progressed to about ten knocks in a row, more frequently, about every five or ten minutes. My husband wants to get a new toilet. Do you think that will do the trick? Is it something that must be fixed before it causes big trouble, or just an annoyance?